Switch Mode Battery Eliminator Based on a PIC16C72A - Microchip

Author: Brett Duane 

Microchip Technology 

OVERVIEW 

The PIC16C72A is a member of the PICmicro ® Mid- 

Range Family of 8-bit, high-speed microcontrollers. 

The PIC16C72 provides the following features: 

• 5 Channel, 8-bit Analog-to-Digital Converter (A/D) 

• CCP Module to generate a PWM output 

• I 2 C/SPI Module 

• 3 Timers 

• 8 Interrupt sources 

This application note shows how to combine the A/D 

and CCP modules with suitable software to produce a 

<strong>Switch</strong> <strong>Mode</strong> <strong>Battery</strong> <strong>Eliminator</strong> (SMBE) providing 3.0, 

4.5, 5.0, 6.0, 7.5 and 9.0 volt output voltages at up to 1 

Amp with an AC or DC input between 12.6V and 30V 

peak. 

HARDWARE 

The system makes use of the A/D to read the input and 

output voltages, the Capture/Compare/Pulse module to 

generate a PWM output, and Timer2 to regulate how 

fast the program runs. External hardware includes a 

switching power converter and a suitable output filter. 

Six LEDs on PORTB indicate the output voltage as set 

by two push buttons on PORTA. 

Optional components not installed in this project 

include a serial EEPROM to store the last voltage setting 

and a level translator to convert TTL to RS-232 for 

communications with a PC. 

In-Circuit Serial Programming (ICSP) support has 

also been provided. LEDs D7 and D8 share clock and 

data lines required for ICSP. These LEDs indicate error 

conditions and are optional. 

AN701 

<strong>Switch</strong> <strong>Mode</strong> <strong>Battery</strong> <strong>Eliminator</strong> <strong>Based</strong> on a PIC16C72A 

Analog-to-Digital Converter Module 

The A/D converts an input voltage between ground and 

VDD to an 8-bit value presented in ADRES. In this application, 

the switching converter input and output voltages 

are sampled. Provisions have been included to 

read the setting of a potentiometer. 

Capture/Compare/Pulse Width Modulation 

Module 

The CCP module produces the PWM signal that controls 

the series pass switching transistor. Depending 

on the PWM period and FOSC, any number of bits 

between 2 and 10 bits may be used to specify the PWM 

on-time. The CCP module requires the use of Timer2, 

the Timer2 prescaler, and the PR2 register to produce 

a PWM output. 

Timer2 Postscaler 

Timer2 drives the CCP module to control the PWM 

period and also drives the Timer2 postscaler. The 

postscaler is incremented when Timer2 is reset at the 

end of each PWM cycle and will generate an interrupt 

when the postscaler overflows. 

External Hardware 

The switching buck converter relies on three components 

to function: 

• Series pass switch (Q1) 

• Inductor (L1) 

• Commutating diode (D10). 

These devices form the core of all switch mode buck 

converters. 

© 1999 Microchip Technology Inc. DS00701A-page 1

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Power Input Circuit 

This circuit is a conventional linear power supply that 

accepts AC or DC power with a peak voltage of 30V 

(limited by the 78L05). The converter operates off the 

unregulated bulk power, while the regulator supplies 

power and a voltage reference to the controller. 

FIGURE 1: POWER INPUT CIRCUIT 

J1 

C5 

.01uF 

BR1 

VUNREG 

C6 

1000uF 

35V 

Figure 1 shows the Power Input Circuit. Bridge rectifier 

BR1 rectifies the raw power input that may be AC or 

DC. Capacitor C6 provides rough filtering to reduce ripple 

in the input voltage. Capacitor C8 provides the short 

current pulses drawn by transistor Q1 when it is turned 

on. Capacitor C7 provides filtering of regulator U2 output. 

C8 

1uF 

35V 

TANT 

DS00701A-page 2 © 1999 Microchip Technology Inc. 

IN 

U2 

LM7805 

OUT 

GND 

+5V 

C7 

10uF 

16V

Power Converter 

Figure 2 shows the switching buck converter with drive 

circuits. Unregulated DC is provided at the emitter of 

transistor Q1. Q1, inductor L1 and diode D10 form the 

basic buck switching converter. The output appears at 

connector J4. 

When RC2 (PWM output) is high, transistor Q2 is 

turned on, pulling Q2’s collector to ground. This draws 

current from Q1’s base, turning Q1 on. When Q1 is on, 

current from capacitors C6 and C8 charge L1 through 

the load. Resistor R19 limits the current drawn from the 

base of Q1. Resistor R17 ensures that Q1 switches off 

quickly. Resistor R20 ensures that transistor Q2 

switches off quickly. Resistor R18 limits Q2’s base current. 

When RC2 is low, R20 turns off Q2 and R17 turns off 

Q1. When Q1 is off, the current through L1 continues to 

flow through L1, D10 and the load, discharging L1. 

When the current through L1 becomes less than the 

current drawn by the load, C10 provides the additional 

current and reduces output voltage ripple. 

AN701 

To ensure that Q1 remains cool during operation, it 

must be driven well into saturation. When driving transistors 

as digital switches, divide their hFE (small signal 

gain) by 5 and use the resulting gain for your calculations. 

This ensures that the transistor switches through 

its linear region quickly to prevent significant heat generation 

in the transistor. 

As the unregulated input voltage decreases, the drive 

applied to Q1 decreases to the point where Q1 starts 

operating in its linear region, producing heat. Continued 

operation in the linear region will cause Q1 to 

overheat and fail. Q1 usually shorts, causing the input 

voltage to appear at the converter output. R19 was 

selected to allow Q1 to operate safely as long as VUN- 

REG is above 10V. The controller software will shut 

down the converter if VUNREG falls below 10V. 

The converter output contains a considerable amount 

of noise. Capacitors C10 and C11 provide filtering to 

reduce that noise. F1 is a PTC resistor acting as a 1 

Amp, self-resetting fuse. 

FIGURE 2: SWITCHING BUCK CONVERTER WITH DRIVE AND OUTPUT CIRCUITS 

PWM 

R18 

1K 

R17 

47 

R20 

220 

Q1 

ZTX751 

R19 

270 

1W 

Q2 

2N2222A 

L1 

100uH 

D10 

1N5822 

C11 

10uF 

35V 

C10 

470uF 

16V 

© 1999 Microchip Technology Inc. DS00701A-page 3 

F1

AN701 

Microcontroller Circuits 

The microcontroller, analog inputs and digital outputs 

are shown in Figure 3. 

The LEDs indicate the output voltage (D1-6) and converter 

faults (D7-8). <strong>Switch</strong>es S1 and S2 allow the user 

to select the desired output voltage. Resistors R3, R4 

and capacitor C4 form the voltage feedback circuit. 

Resistors R15, R16 and capacitor C13 form the voltage 

source sense circuit. PWM is output at pin RC2. 

Register packs RN5 and RN6 limit current through 

LEDs D1-D8. LEDs D7 and D8 share clock and data 

lines required for ICSP. Jumper J1 disables all LEDs. 

When programming the controller using ICSP, J1 

should be removed. If ICSP does not function properly, 

D7 and D8 or RN6 should be installed after programming. 

S1 is the decrease voltage button and S2 is the 

increase voltage button. R13 and R14 are pull down 

resistors. 

Resonator Y1, and capacitors C2 and C3 set Fosc for 

the controller. If Y1 is a ceramic resonator with internal 

capacitors, C2 and C3 are not required. Resistor R1 

pulls MCLR to +5V while allowing the controller to be 

programmed using ICSP. In addition, connecting pins 1 

and 3 of connector J2 causes a remote reset of the controller. 

(See figure 5.) 

FIGURE 3: MICROCONTROLLER, ANALOG INPUTS AND DIGITAL INPUTS AND OUTPUTS 

R2 

5K 

VOUT 

R3 

1K 

R4 

1K 

+5V 

VUNREG 

R16 

5.6K 

C4 

.01uF 

R15 

1K 

R1 

10K 

+5V 

C12 

.01uF 

Y1, 10MHz 

Resonator 

C2 

20pF 

C1 

.1uF 

C13 

.01uF 

C3 

20pF 

MCLR 

RA2 

RA5 

PIC16C72A 

UP DN 


RB6 

RB7 

PWM 

SCL 

SDA 

RC5 

RC6 

RC7 

RN5 

470 

RN6 

+5V 

470 

RA5 

RA2 

R13 

5.6K 

R14 

5.6K 

JP1

FIRMWARE 

Initialization 

The controller is first initialized by configuring the A/D, 

CCP and Timer2 peripherals, followed by clearing the 

RAM required for variables and initializing some variables. 

Controller pins are configured as required for 

each of the modules, or as digital outputs if they are not 

being used. 

A/D 

Pins RA0, RA1 and RA3 are configured as analog 

inputs. Pins RA2 and RA5 are used as digital inputs. 

The controller VDD is used as VREF for the A/D. 

The conversion clock source TAD is selected to be 

between 1.6usec and 6.4usec. Since Tosc = 0.1usec 

(Fosc = 10MHz), 32Tosc = 3.2usec. The A/D module is 

turned on and pin RA1 (VOUT) is sampled for conversion 

later in the loop. 

TRISA configures pin RA4 as an output and all others 

as inputs. 

CCP (PWM) 

The CCP module is set to PWM mode. Timer2 is 

enabled with a 1:1 prescaler. PR2 is set to 63 (0x3F). 

The resulting PWM frequency is 39.063KHz. 

(TPWM=25.6msec). The CCP module uses 8-bit data 

to control the PWM duty cycle. The PWM duty cycle is 

set to 0, ensuring that the PWM output is turned off. 

All pins on PORTC are configured as outputs, including 

RC2 which is the controller PWM output. 

Timer2 postscaler 

Since Timer2 will also control the frequency that the 

main loop will execute, the Timer2 postscaler is set to a 

1:1 ratio and the Timer2 postscaler interrupt is enabled. 

This will cause one interrupt for each PWM cycle. 

RAM 

RAM required for variables is cleared. The 3.0V LED 

on PORTB is lit. The variable set_pt is initialized to 

produce the 3.0V output. Button debounce counters 

are initialized. 

Main loop 

For a digital control loop to function as well as an analog 

controller, the digital control loop should repeat at 

least 30 times faster than the fastest expected transient. 

The ripple frequency at capacitor C7 is 120Hz, or twice 

the AC power line frequency. In this application, the 

loop must be executed at least 120 x 30, or 3600 times 

a second to adequately respond to the bulk power ripple. 

Transients at the converter output are also handled, 

but less effectively with increasing frequency. 

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The Timer2 postscaler generates interrupts that are 

counted by the interrupt service routine. When 8 interrupts 

have occurred, the main loop is allowed to execute 

once. This causes the main loop to execute 4883 

times a second. 

The A/D starts a conversion on RA1/AN1 (VOUT). The 

program loops wait for the conversion to complete. The 

8-bit result is placed in VOUT. The A/D is then set to 

sample the input voltage (VUNREG). 

PID Controller 

The control algorithm is a software implementation of a 

Proportional-Integral-Differential (PID) controller. The 

only input to this controller is the difference between the 

desired output voltage and the actual output voltage, 

and is known as the error signal. 

The first module produces the error signal by finding 

the difference between set_pt and VOUT. The result 

is saved in the low byte of a 2 byte signed variable 

e0h:e0. The high byte is set to reflect a negative value 

if needed. The difference is selected to produce a positive 

result if set_pt is greater than VOUT. 

e0 = set_pt - vout 

if e0=0 , e0h = 0x00, else e0h = 0xFF 

A proportional term is generated from the present error 

signal. This is simply the signed error multiplied by 

some factor Kp. The 2 byte signed result is saved as 

proh:pro. 

proh:pro = Kp * e0h:e0 

Kp = proportional factor 

The difference between the present and previous error 

is found and saved as the 2 byte signed result 

difh:dif. The previous error e1h:e1 is simply the 

error result found in the execution of the previous loop. 

The difference between errors is multiplied by some 

factor (Kd) and saved as difh:dif. 

difh:dif = Kd * (e1h:e1 – e0h:e0) 

Kd=difference factor 

The integral component is nothing more than a total of 

all the errors produced since the last reset. The present 

error is multiplied by some factor (Ki) before being 

added to the running 2 byte unsigned total inth:int. 

inth:int = inth:int + Ki * e0h:e0 

Ki = integral factor 

The proportional, integral and difference terms are 

summed together. The result of the sum is saved as the 

2 byte signed result pwmh:pwm. 

pwmh:pwm = proh:pro + difh:dif 

+ inth:int 


AN701 

The result is never greatly positive, but can sometimes 

cause the result to underflow. When pwmh:pwm underflows 

(as it does when the load is disconnected), the 

PWM drive signal must be forced to zero or the converter 

output becomes unpredictable. The overload 

LED is also lit. 

If pwmh = 1, then pwmh:pwm = 0x0000 and turn 

on the OVLD LED, else turn off OVLD LED. 

PWM Generator 

The PWM generator module (software, not the peripheral) 

discards the 3 least and 5 most significant bits, 

and uses the remaining 8 bits to generate PWM with a 

desired on time. Of the remaining 8 bits, the 2 least significant 

bits are loaded into CCP1CON. The last 

6 bits (with 2 leading zeros to form a byte) are loaded 

into CCP1RL. 

Conversion of the input voltage VUNREG is started. 

Reading Buttons 

The LED data at PORTB is copied to a temporary variable. 

The down button is read. If it is closed, its debounce 

counter is incremented. If no overflow occurs, execution 

proceeds to reading the up button. If an overflow 

does occur, the LED data is shifted right one bit, unless 

bit 0 is already set. Overflows occur approximately 

every half second. 

The up button is read and processed similar to the 

down button. If it is closed, its debounce counter is 

incremented. If no overflow occurs, execution proceeds 

to convert VIN. If an overflow does occur, the 

LED data is shifted left one bit, unless bit 5 is already 

set. Overflows occur approximately every half second. 

The LED data is copied back to PORTB to light the corresponding 

LED. The LED data is also used to find the 

proper index to use prior to calling a look-up table. 

A call to the lookup table is performed. The lookup 

table routine adds the index in the W register to the program 

counter. The next instruction performed is a 

"retlw" instruction that places the new set_pt in the 

W register and returns to the next instruction after the 

call to the look-up table. The value returned is saved 

as the new set_pt. 

Both button debounce counters are reset. 

The conversion result of VIN is retrieved from the A/D 

and vin is subtracted from 0xC1 (10V set point). If the 

result is positive, VIN is less than 10V and program execution 

is directed to a safety shutdown module. Otherwise, 

program execution continues normally. 

If (0xC1 – vin) is positive, go to shutdown. 

The present error, e0h:e0, replaces the previous 

error, e1h:e1. 

Program execution then returns to the top of the loop to 

wait for Timer2 postscaler interrupts. 

Interrupts 

The Interrupt Service Routine saves the state of the W 

and STATUS registers, increments the interrupt counter 

and restores the STATUS and W registers. 

Safety Shutdown 

The safety shutdown module has been included to turn 

off the converter and to light the trip LED. Once 

entered, there is no exit from this module except by 

resetting the controller. 

Gain constants Kp, Kd, and Ki 

Constants Kp, Ki, and Kd were determined experimentally. 

The goal was to maintain VOUT between 4.75V 

and 5.25V when the 5V output was selected. VOUT 

should remain within this band, regardless of changes 

in the load current. This specifically includes 10% 

changes in current, unloaded to full-load, and full-load 

to unloaded step changes. Other step changes in loading 

were also examined. 

Constants determined for a 5V output were then used 

for other voltage outputs. 

Only resistive loads were considered. Some degradation 

of output performance may be expected with inductive 

or capacitive loads. 

DS00701A-page 6 © 1999 Microchip Technology Inc.

APPENDIX A: SWITCH MODE BUCK 

CONVERTER 

A switch mode buck converter performs a voltage 

reduction by periodically charging an inductor from a 

high voltage source, then allowing the charged inductor 

to transfer its stored energy to the load at a lower voltage. 

This energy transfer occurs with little loss. 

FIGURE 4: SWITCH MODE BUCK 

CONVERTER TOPOLOGY 

Input 

L 

Output 

Q 

D C R 

In the ideal buck converter, the average output power 

equals the average input power. The switch is operated 

at a constant frequency, but the duty cycle (on time / 

cycle time) controls the output voltage. 

When the switch Q (a transistor or MOSFET) is closed, 

current from the source flows through the inductor L, 

through the load R and back to the source. Energy is 

being stored in the inductor by increasing inductor current 

and building up a magnetic field. 

When the switch is open, the source no longer supplies 

energy. The energy stored in the magnetic field is 

transferred to the load as the magnetic field collapses. 

Inductor current is decreasing as current flows from the 

inductor through the load R and diode D and back to 

the inductor L. 

No energy is lost in the inductor during this conversion. 

The majority of losses occur in the switching device as 

it switches though its linear region, and the commutation 

diode when it conducts due to its forward voltage 

drop. Most electrolytic filter capacitors also have high 

resistance to the high frequency ripple current. 

If current flows through the inductor at all times, the 

converter is operating in the continuous mode. The 

average inductor current is the same as the load current. 

If the load current is constant, variations in the 

inductor current average to zero. The peak inductor 

current will be no greater than twice the average current, 

and can be reduced by raising the switching frequency. 

This is normally the desired operating mode. 

If the current through the inductor stops, the converter 

is operating in the discontinuous mode. All the current 

that flows through the load continuously must flow 

through the switch and charge the inductor during the 

time the switch is turned on. This can result in very high 

currents in both the switch and inductor and risks saturating 

the inductor. When the inductor is saturated, its 

inductance decreases drastically. Considerable noise 

is also produced as large currents are switched, requiring 

a greater amount of filtering. This mode is normally 

AN701 

used only when there is very light loading of the converter, 

but it is easier to stabilize than the continuous 

mode converter. 

In both continuous and discontinuous modes, charging 

or discharging a filter capacitor at the converter output 

makes up the difference between the inductor and load 

currents. This filter capacitor also reduces output ripple 

voltage and noise that switching converters produce. 

The equations presented here assume an ideal circuit, 

but actual circuits have similar results. 

The approximate duty cycle D.C. can be approximated 

by: 

D.C. = VOUT = IIN = TON 

VIN IOUT TPWM 

Where VOUT = output voltage, 

IIN = average input current, 

TON = switch on time 

VIN = input voltage, 

IOUT = output current, 

TPWM = PWM period = 1/FPWM 

The ripple current magnitude due to switching is 

approximated by: 

IRIPPLE = (VIN-VOUT) * D.C. * TPWM 

L 

Where L = inductor inductance, 

IRIPPLE = ripple current peak-to-peak 

FPWM = PWM frequency 

The ripple current is absorbed by the output filter 

capacitor C, but produces a small output ripple voltage 

that is approximated by: 

VRIPPLE = IRIPPLE * D.C. * TPWM 

C 

Where VRIPPLE = output voltage ripple peak-to-peak 

EXAMPLE 1: CAPACITOR AND 

INDUCTOR SELECTION 

Given: VUNREG = 20V, VOUT = 6V, 

VRIPPLE = 0.1V, IRIPPLE = 1A, 

FPWM = 39.063KHz 

Solution: 

D.C. = VOUT = 6 = 0.30 

VIN 20 

TPWM = 1 = 1 = 25.6uS 

FPWM 39KHz 

C = IRIP*D.C.*TPWM = (1A)(.3)(25.6uS) 

VRIPPLE 0.1V 

= 76.8uF 

IRIP = (VIN-VOUT)*D.C.*TPWM 

L 

L = (VIN-VOUT)*D.C.*TPWM 

© 1999 Microchip Technology Inc. DS00701A-page 7 

IRIP 

= (20V-6V)(0.30)(25.6uS) 

1A 

= 107.5uH

AN701 

APPENDIX B: ACCESSORY 

COMPONENTS 

These accessory component are not installed on the 

board, but can provide additional capabilities. Connector 

J2 provides for In-Circuit Serial Programming 

(ICSP) and offers a remote MCLR reset by connecting 

FIGURE 5: ACCESSORY COMPONENTS 

+5V 

MCLR 

RB7 

RB6 

J2 

+5V 

R21 

4.7K 

SCL 

+5V 

J3 

VCC 

SCL 

WP 

GND 

C29 

.1uF 

pins 1 and 3. Integrated circuit U3 and connector J3 

provide RS-232 communications with the controller. 

Integrated circuit U4 is a serial EEPROM that communicates 

with the controller using the I 2 C protocol. 


C16 

.1uF 

U4 

24LC01BD 

R31 

10 

SDA 

A0 

A1 

A2 

+5V 

VCC 

RXin 

NC 

TXout 

U3 

DS275 

RXout 

Vdrv 

TXin 

GND 

+5V 

R22 

4.7K 

SDA 

RC7 

RC6 

+5V

APPENDIX C: CODE 

MPASM 02.20 Released SW_REG1A.ASM 3-9-1999 19:28:40 

LOC OBJECT CODE LINE SOURCE TEXT 

VALUE 

AN701 

00001 

;**************************************************************************** 

00002 ;* Filename: APPNOTE.ASM 

00003 

;**************************************************************************** 

00004 ;* Author: Brett Duane 

00005 ;* Company: Microchip Technology 

00006 ;* Revision: Rev 1.0 

00007 ;* Date: 3-9-99 

00008 ;* Assembled using MPASM rev 4.00.00 

00009 

;**************************************************************************** 

00010 ;* Include files: p16c72a.inc Rev 1.01 

00011 

;**************************************************************************** 

00012 ;* 

00013 ;* <strong>Switch</strong>ing buck regulator using 16C72A using A/D, 

00014 ;* PWM (CCP) and timer2 modules. 

00015 ;* 

00016 ;* PID control loop implementation. 

00017 ;* Executes 4883 loops per second. 

00018 ;* Spends most of its time looping waiting for timer2 overflows. 

00019 ;* 

00020 ;* A/D inputs and PWM output are 8 bits, 

00021 ;* with internal calculations done in 16 bits 

00022 ;* 

00023 ;* Timer2 postscaler (1:16) generates an interrupt. 

00024 ;* 

00025 ;* RA0 converts a 0-5V input from trimmer, but is not used. 

00026 ;* RA1 monitors VOUT. 

00027 ;* RA2 is the up voltage push button input. 

00028 ;* RA3 monitors VUNREG. 

00029 ;* RA5 is the down voltage push button input. 

00030 ;* 

00031 ;* RB drives LEDs to indicate the output voltage. 

00032 ;* RB drives LEDs to indicate overload or shutdown. 

00033 ;* 

00034 ;* RC2 is the PWM source for the switching converter. 

00035 ;* 

00036 ;* 

00037 ;* Configuration Bit Settings 

00038 ;* Brown-out detect is off 

00039 ;* Code protect is off 

00040 ;* Power-up timer is enabled 

00041 ;* Watchdog timer is disabled 

00042 ;* 10MHz resonator is driven in XT mode 

00043 ;* 

00044 ;* Program Memory Words Used: 230 

00045 ;* Program Memory Words Free: 1818 

00046 ;* 

00047 ;* Data Memory Bytes Used: 24 

00048 ;* Data Memory Bytes Free: 104 

00049 ;* 

00050 

;**************************************************************************** 

00051 ;* What’s Changed 

00052 ;* 

00053 ;* Date Description of Change 


AN701 

00054 ;* 

00055 ;* 3-3-99 This is the initial release. 

00056 ;* 

00057 

;**************************************************************************** 

00058 

00059 list p=16c72a 

00060 #include 

00001 LIST 

00002 ; P16C72A.INC Standard Header File,Version 1.01 Microchip Technology, Inc. 

00249 LIST 

00061 

2007 3FB1 00062 __config _BODEN_OFF & _CP_OFF & _PWRTE_ON & _WDT_OFF & _XT_OSC 

00063 

00064 

00065 cblock 0x020 

00066 

00000020 00067 UPCL ;up button debounce 

00000021 00068 UPCH ;up button debounce 

00000022 00069 DNCL ;down button debounce 

00000023 00070 DNCH ;down button debounce 

00000024 00071 SETPOINT ;voltage setpoint - RA0 result (unsigned) 

00000025 00072 VOUT ;output voltage feedback - RA1 result 

00000026 00073 VUNREG ;source voltage feedback - RA3 result 

00000027 00074 TEMPA ;temp variable 

00000028 00075 TEMPB ;temp variable 

00000029 00076 INT ;integral component 

0000002A 00077 INTH ;integral component 

0000002B 00078 PRO ;proportional component 

0000002C 00079 PROH ;proportional component 

0000002D 00080 DIF ;difference component 

0000002E 00081 DIFH ;difference component 

0000002F 00082 PWM ;PWM drive 

00000030 00083 PWMH ;PWM drive 

00000031 00084 E0 ;present error 

00000032 00085 E0H ;present error 

00000033 00086 E1 ;past error 

00000034 00087 E1H ;past error 

00000035 00088 T2POST ;postscaler interrupt counter 

00000036 00089 ISRS ;isr variable 

00000037 00090 ISRW ;isr variable 

00091 

00092 endc 

00093 

000000F9 00094 DEL1 equ 0xf9 ;text equate - debounce delay 

00000089 00095 AVOUT equ 0x89 ;text equate - select VOUT channel 

00000099 00096 AVUNREG equ 0x99 ;text equate - select VUNREG channel 

00097 

00098 

;**************************************************************************** 

00099 ;* Reset vector 

00100 ;* This is the reset vector 

00101 ;* 

00102 

;**************************************************************************** 

00103 

0000 00104 org 0x00 ;reset vector 

0000 280E 00105 goto Main ;program start 

00106 

00107 

00108 

;**************************************************************************** 

00109 ;* INTERRUPT SERVICE ROUTINE 

00110 ;* This ISR counts timer2 interrupts 

00111 ;* 

00112 ;* Input Variables: 


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00113 ;* T2POST Counts overflow interrupts 

00114 ;* 

00115 ;* Output Variables: 

00116 ;* T2POST Counts overflow interrupts 

00117 ;* 

00118 

;**************************************************************************** 

00119 

0004 00120 org 0x04 ;interrupt service routine 

00121 

0004 00B7 00122 movwf ISRW ;save W 

0005 0E03 00123 swapf STATUS,W ;get status 

0006 00B6 00124 movwf ISRS ;save status 

00125 

0007 108C 00126 bcf PIR1,TMR2IF;clear interrupt request flag 

00127 

0008 0AB5 00128 incf T2POST,F ;increment interrupt counter 

00129 

0009 0E36 00130 swapf ISRS,W ;get status 

000A 0083 00131 movwf STATUS ;restore status 

000B 0EB7 00132 swapf ISRW,F ;restore W 

000C 0E37 00133 swapf ISRW,W ;restore W 

00134 

000D 0009 00135 retfie ;return from interrupt 

00136 

00137 

;**************************************************************************** 

00138 ;* Main Beginning of main loop 

00139 ;* First segment of code initializes controller 

00140 

;**************************************************************************** 

00141 

000E 00142 Main 

000E 1303 00143 bcf STATUS,RP1;bank1 initialization 

000F 1683 00144 bsf STATUS,RP0;bank1 

00145 ;adc 

0010 3004 00146 movlw 0x04 ;RA0,1,3 analog, RA2,5 digital, Vref=Vdd 

0011 009F 00147 movwf ADCON1 

00148 

0012 302F 00149 movlw 0x2f ;RA0,1,3 analog in; RA2,5 digital in, RA4 dig out 

0013 0085 00150 movwf TRISA 

00151 ;PWM 

0014 30FF 00152 movlw 0xFF ;set portC to all inputs 

0015 0087 00153 movwf TRISC 

0016 1107 00154 bcf TRISC,2 ;make RC2/PWM output 

00155 

0017 303F 00156 movlw .63 ;PWM period = 78.125KHz (8 bit resolution) 

0018 0092 00157 movwf PR2 

00158 

00159 ;timer2 

0019 148C 00160 bsf PIE1,TMR2IE;enable timer2 postscaler interrupts 

00161 

00162 ;display 

001A 0186 00163 clrf TRISB ;make PORTB all outputs 

00164 

001B 1283 00165 bcf STATUS,RP0;select bank0 

00166 ;adc 

001C 3089 00167 movlw AVOUT ;(10MHz osc)set A/D conv clock(Fosc/32), 

001D 009F 00168 movwf ADCON0 ;select RA1(AN1), turn on A/D 

00169 ;PWM 

001E 1217 00170 bcf CCP1CON,4;clear ls bits of PWM duty cycle 

001F 1297 00171 bcf CCP1CON,5 

0020 0195 00172 clrf CCPR1L ;set PWM to 0 (turn off PWM) 

00173 

0021 3004 00174 movlw 0x04 ;enable timer2, set prescale=1:1, 

postscale=1:1 


AN701 

0022 0092 00175 movwf T2CON 

0023 300C 00176 movlw 0x0C ;set CCP1 to PWM mode 

0024 0097 00177 movwf CCP1CON 

00178 

00179 ;**************************************************************************** 

00180 ;* Restart Clears memory 

00181 ;* 

00182 ;* Initializes display LEDs, desired output voltage, 

00183 ;* debounce counters 

00184 ;* 

00185 ;* Enables interrupts 

00186 ;* 


00188 ;* SETPOINT desired output voltage, set to 3.0V 

00189 ;* DNCL, DNCH Down voltage button debounce counter 

00190 ;* UPCL, UPCH Up voltage button debounce counter 

00191 ;* 

00192 ;**************************************************************************** 

00193 

0025 3020 00194 Restart movlw 0x20 ;clear memory from 0x20 to 0x3f 

0026 0084 00195 movwf FSR 

0027 0180 00196 ClrMem clrf INDF 

0028 0A84 00197 incf FSR,F 

0029 1F04 00198 btfss FSR,6 

002A 2827 00199 goto ClrMem 

00200 

002B 3001 00201 movlw 0x01 ;light 3.0V LED 

002C 0086 00202 movwf PORTB 

00203 

002D 304D 00204 movlw 0x4d ;initial 3.0V setting 

002E 00A4 00205 movwf SETPOINT 

00206 

002F 01A2 00207 clrf DNCL ;clear down button debounce counter 

0030 01A0 00208 clrf UPCL ;clear up button debounce counter 

00209 

0031 30F9 00210 movlw DEL1 

0032 00A3 00211 movwf DNCH ;preset down button debounce counter byte 

0033 00A1 00212 movwf UPCH ;preset up button debounce counter high byte 

00213 

0034 170B 00214 bsf INTCON,PEIE ;enable peripheral interrupt sources 

0035 178B 00215 bsf INTCON,GIE ;enable all interrupts 

00216 

00217 ;**************************************************************************** 

00218 ;* 

00219 ;* Again Top of main loop 

00220 ;* 

00221 ;* Waits for 8 timer2 interrupts 

00222 ;* 

00223 ;* A/D converts VOUT 

00224 ;* 

00225 ;* Acquires VUNREG channel 

00226 ;* 


00228 ;* T2POST Timer2 interrupt counter 

00229 ;* 


00231 ;* VOUT Conversion result 

00232 ;* 

00233 ;**************************************************************************** 

00234 

0036 00235 Again 

0036 1DB5 00236 btfss T2POST,3 ;long delay 

0037 2836 00237 goto Again ;try again 

00238 

0038 01B5 00239 clrf T2POST ;clear counter 

00240 


00241 ;--- start conversion - feedback 

0039 151F 00242 bsf ADCON0,GO_DONE ;start conversion 

003A 0000 00243 nop 

003B 191F 00244 Wc2 btfsc ADCON0,GO_DONE ;test if done 

003C 283B 00245 goto Wc2 ;no, wait some more 

003D 081E 00246 movf ADRES,W ;get conversion result 

003E 00A5 00247 movwf VOUT ;save result 

00248 ;--- end conversion 

003F 3099 00249 movlw AVUNREG ;select VUNREG channel 

0040 009F 00250 movwf ADCON0 

00251 

00252 

;**************************************************************************** 

00253 ;* FErr Finds difference (error) between SETPOINT and VOUT 

00254 ;* E0H:E0 = SETPOINT - VOUT 

00255 ;* 


00257 ;* SETPOINT Desired output voltage 

00258 ;* 


00260 ;* E0H:E0 Signed error 

00261 

;**************************************************************************** 

00262 

0041 00263 FErr 

0041 01B2 00264 clrf E0H ;clear error high byte 

00265 

0042 0825 00266 movf VOUT,W 

0043 0224 00267 subwf SETPOINT,W ;f-w=d 

0044 00B1 00268 movwf E0 ;save new error 

00269 

0045 1C03 00270 btfss STATUS,C ;was there a borrow? 

0046 09B2 00271 comf E0H,F ;yes 

00272 

00273 

;**************************************************************************** 

00274 ;* Ppp Produces proportional term by multiplying E0H:E0 by Kp 

00275 ;* 

00276 ;* PROH:PRO = E0H:E0 * Kp 

00277 ;* Kp = 2^3 - Produced by 3 left shifts 

00278 ;* 

00279 ;* This term forces the output close to the desired output 

00280 ;* quickly, but will never completely eliminate the error. 

00281 ;* 


00283 ;* E0H:E0 Error found at top of loop 

00284 ;* Kp Proportional gain factor (constant) 

00285 ;* 


00287 ;* PROH:PRO Proportional component 

00288 ;* 

00289 

;**************************************************************************** 

00290 

0047 00291 Ppp 

0047 0831 00292 movf E0,W ;move E0 to temp space 

0048 00A7 00293 movwf TEMPA 

0049 0832 00294 movf E0H,W 

004A 00A8 00295 movwf TEMPB 

00296 

004B 1003 00297 bcf STATUS,C ;mult E0 by 2 

004C 0DA7 00298 rlf TEMPA,F 

004D 0DA8 00299 rlf TEMPB,F 

00300 

004E 1003 00301 bcf STATUS,C ;mult E0 by 2 

004F 0DA7 00302 rlf TEMPA,F 

AN701 


AN701 

0050 0DA8 00303 rlf TEMPB,F 

00304 

0051 1003 00305 bcf STATUS,C ;mult E0 by 2 

0052 0DA7 00306 rlf TEMPA,F 

0053 0DA8 00307 rlf TEMPB,F 

00308 

0054 0827 00309 PppD movf TEMPA,W ;move result in temp space to pro 

0055 00AB 00310 movwf PRO 

0056 0828 00311 movf TEMPB,W 

0057 00AC 00312 movwf PROH 

00313 

00314 

;**************************************************************************** 

00315 ;* DifCom Computes differential component 

00316 ;* 

00317 ;* Finds difference between this loop error and previous 

loop error 

00318 ;* DIFH:DIF = (E1H:E1 - E0H:E0) * Kd 

00319 ;* 

00320 ;* Kd = 2^3 - Produced by 3 left shifts 

00322 ;* This term tends to slow controller response. 

00323 ;* 


00325 ;* E1H:E1 Previous loop error 

00326 ;* E0H:E0 Present loop error 

00327 ;* Kd Differential gain factor (constant) 

00328 ;* 


00330 ;* DIFH:DIF differential component 

00331 ;* 

00332 

;**************************************************************************** 

00333 

0058 00334 DifCom 

0058 0834 00335 movf E1H,W ;get prev error high byte 

0059 0232 00336 subwf E0H,W ;f-w=d E0-E1=w 

005A 00AE 00337 movwf DIFH ;save difference high byte 

00338 

005B 0833 00339 movf E1,W ;get prev error low byte 

005C 0231 00340 subwf E0,W ;f-w=d E0-E1=w 

005D 00AD 00341 movwf DIF ;save difference low byte 

00342 

005E 1C03 00343 btfss STATUS,C ;was there a borrow? 

005F 03AE 00344 decf DIFH,F ;yes 

00345 

00346 ;allow difference to be modified here 

00347 

0060 1003 00348 bcf STATUS,C ;mult dif by 2 

0061 0DAD 00349 rlf DIF,F 

0062 0DAE 00350 rlf DIFH,F 

00351 


0064 0DAD 00353 rlf DIF,F 


00355 


0067 0DAD 00357 rlf DIF,F 


00359 

00360 

00361 

00362 

;**************************************************************************** 

00363 ;* IntCom Computes integral component 

00364 ;* 

00365 ;* Multiplies present error by Ki, 


00366 ;* adds result to INTH:INT 

00367 ;* 

00368 ;* INTH:INT = INTH:INT + E0H:E0 * Ki 

00369 ;* 

00370 ;* Ki = 2^3 -- Produced by 3 left shifts 

00371 ;* 

00372 ;* This term will eliminate all error, 

00373 ;* but not quickly 

00374 ;* 


00376 ;* E0H:E0 Present loop error 

00377 ;* INTH:INT Running total of errors 

00378 ;* Ki Integral gain factor (constant) 

00379 ;* 


00381 ;* DIFH:DIF differential component 

00382 

;**************************************************************************** 

00383 

0069 00384 IntCom 

0069 0832 00385 movf E0H,W ;move E0 to temp space 

006A 00A8 00386 movwf TEMPB 

006B 0831 00387 movf E0,W 

006C 00A7 00388 movwf TEMPA 

00389 

00390 ;allow error to be modified here before adding to integral 

00391 

006D 1003 00392 bcf STATUS,C 

006E 0DA7 00393 rlf TEMPA,F ;E0 

006F 0DA8 00394 rlf TEMPB,F ;E0H 

00395 

0070 1003 00396 bcf STATUS,C 

0071 0DA7 00397 rlf TEMPA,F ;E0 

0072 0DA8 00398 rlf TEMPB,F ;E0H 

00399 

0073 1003 00400 bcf STATUS,C 

0074 0DA7 00401 rlf TEMPA,F ;E0 

0075 0DA8 00402 rlf TEMPB,F ;E0H 

00403 

0076 0827 00404 IntD movf TEMPA,W ;get current error, E0 

0077 07A9 00405 addwf INT,F ;add to INT, store in INT 

0078 1803 00406 btfsc STATUS,C ;was there a carry? 

0079 0AAA 00407 incf INTH,F ;yes, inc INT high byte 

00408 

007A 0828 00409 movf TEMPB,W ;get E0 high byte, E0H 

007B 07AA 00410 addwf INTH,F 

00411 

00412 

;**************************************************************************** 

00413 ;* Total Sums proportional, integral, and differential terms 

00414 ;* 

00415 ;* PWMH:PWM = INTH:INT + PROH:PRO + DIFH:DIF 

00416 ;* 

00417 ;* If the result should ever go negative, 

00418 ;* the result is forced to 0,and the overload LED is set. 

00419 ;* (This is an error condition.Can’t have a negative PWM.) 

00420 ;* 


00422 ;* INTH:INT Integral term 

00423 ;* PROH:PRO Proportional term 

00424 ;* DIFH:DIF Differential term 

00425 ;* 


00427 ;* PWMH:PWM Sum of terms 

00428 

;**************************************************************************** 

AN701 


AN701 

00429 

007C 00430 Total 

007C 082C 00431 PCom movf PROH,W ;add in proportional term 

007D 00B0 00432 movwf PWMH 

00433 

007E 082B 00434 movf PRO,W 

007F 00AF 00435 movwf PWM 

00436 

0080 082A 00437 ICom movf INTH,W ;add in integral term 

0081 07B0 00438 addwf PWMH,F 

00439 

0082 0829 00440 movf INT,W 

0083 07AF 00441 addwf PWM,F 

0084 1803 00442 btfsc STATUS,C 

0085 0AB0 00443 incf PWMH,F 

00444 

0086 082E 00445 DCom movf DIFH,W ;add in differential term 

0087 07B0 00446 addwf PWMH,F 

00447 

0088 082D 00448 movf DIF,W 

0089 07AF 00449 addwf PWM,F 

008A 1803 00450 btfsc STATUS,C 

008B 0AB0 00451 incf PWMH,F 

00452 

008C 1BB0 00453 Ovrld btfsc PWMH,7 ;did PWM go negative? 

008D 2890 00454 goto NegPwm ;yes 

008E 1306 00455 bcf PORTB,6 ;no - turn off overload LED 

008F 2893 00456 goto PwmGen 

00457 

0090 1706 00458 NegPwm bsf PORTB,6 ;turn on overload LED 

0091 01B0 00459 clrf PWMH ;set PWM to 0 

0092 01AF 00460 clrf PWM 

00461 

00462 

;**************************************************************************** 

00463 ;* PwmGen Divides PWHM:PWM by 8 (3 right shifts) 

00464 ;* 2 LSbits of PWM sent to 2 LSbits of duty cycle register 

00465 ;* remaining 6 bits sent to CCPR1L (duty cycle register) 

00466 ;* 

00467 ;* A/D has been acquiring VUNREG, start conversion. 

00468 ;* 


00470 ;* PWMH:PWM PWM drive 

00471 

;**************************************************************************** 

00472 

009 00473 PwmGen 

0093 0CB0 00474 rrf PWMH,F ;PWMH 

0094 0CAF 00475 rrf PWM,F ;PWM 

00476 

0095 0CB0 00477 rrf PWMH,F ;PWMH 


00479 

0097 0CB0 00480 rrf PWMH,F ;PWMH - can ignore contents of PWMH now 


00482 

0099 1217 00483 bcf CCP1CON,4 ;clear ls bits of PWM duty cycle 

009A 1297 00484 bcf CCP1CON,5 

00485 

009B 0CAF 00486 rrf PWM,F ;shift carry INTo PWM, lsbit INTo carry 

009C 1803 00487 btfsc STATUS,C ;is carry set? 

009D 1617 00488 bsf CCP1CON,4 ;set PWM duty cycle lsb 

00489 

009E 0CAF 00490 rrf PWM,F ;shift carry INTo PWM, lsbit INTo carry 

009F 1803 00491 btfsc STATUS,C ;is carry set? 

00A0 1697 00492 bsf CCP1CON,5 ;set PWM duty cycle lsb 


AN701 

00493 

00A1 082F 00494 movf PWM,W ;get PWM 

00A2 393F 00495 andlw 0x3f ;mask off 2 ms bits (78.125KHz) 

00A3 0095 00496 movwf CCPR1L ;put in PWM duty cycle 

00497 

00A4 151F 00498 bsf ADCON0,2 ;start conversion VUNREG 

00499 

00500 

;**************************************************************************** 

00501 ;* up/dn buttons 

00502 ;* Debounces UP and DOWN buttons 

00503 ;* Increments counters once for each pass 

00504 ;* through the loop when button pressed. 

00505 ;* 

00506 ;* If button not pressed, counter is reset. 

00507 ;* 

00508 ;* If a button is successfully debounced, 

00509 ;* both counters are reset. 

00510 ;* 

00511 ;* Debounce delay is about 0.5 seconds 

00512 ;* 

00513 ;* Moves voltage indicator bit as required. 

00514 ;* 

00515 ;* Finds index into lookup table, and calls table. 

00516 ;* 

00517 ;* Saves result from lookup table as new SETPOINT 

00518 ;* 


00520 ;* PORTB Current indicator data 

00521 ;* DNCH:DNCL Down button debounce counter 

00522 ;* UPCH:UPCL Up button debounce counter 

00523 ;* 


00525 ;* PORTB Current indicator data 

00526 ;* DNCH:DNCL Down button debounce counter 

00527 ;* UPCH:UPCL Up button debounce counter 

00528 ;* SETPOINT New voltage setpoint 

00529 

;**************************************************************************** 

00530 

00A5 0806 00531 movf PORTB,W ;move LED data to temp space 

00A6 393F 00532 andlw 0x3f ;mask off non-voltage LEDs 

00A7 00A7 00533 movwf TEMPA 

00534 

00A8 1E85 00535 Dnb btfss PORTA,5 ;down 

00A9 28B3 00536 goto Upb ;down not pushed 

00AA 0FA2 00537 incfsz DNCL,f ;down is pushed, inc debounce 

00AB 28CE 00538 goto Wc3 ;no carry - go to next module 

00AC 0FA3 00539 incfsz DNCH,f ;inc debounce counter high byte 

00AD 28CE 00540 goto Wc3 ;no carry - go to next module 

00541 ;---------------------- select next lower LED 

00AE 1003 00542 bcf STATUS,C ;select next lower LED 

00AF 0CA7 00543 rrf TEMPA,F ;shift LED data down 1 voltage 

00B0 1803 00544 btfsc STATUS,C ;3V LED was set before rotate, so 

00B1 1427 00545 bsf TEMPA,0 ;set it again 

00546 

00B2 28BE 00547 goto Dunb 

00548 

00B3 1D05 00549 Upb btfss PORTA,2 ;up button 

00B4 28C9 00550 goto Nob ;up not pushed - no buttons pushed 

00B5 0FA0 00551 incfsz UPCL,f ;down is pushed, inc debounce 

00B6 28CE 00552 goto Wc3 ;no carry - go to next module 

00B7 0FA1 00553 incfsz UPCH,F ;inc debounce counter high byte 

00B8 28CE 00554 goto Wc3 ;no carry - go to next module 

00555 ;-------------------- select next higher LED 

00B9 1003 00556 bcf STATUS,C ;select next higher voltage LED 


AN701 

00BA 0DA7 00557 rlf TEMPA,F ;shift LED data up 1 voltage 

00BB 1B27 00558 btfsc TEMPA,6 ;if 9V LED was set before, 

00BC 16A7 00559 bsf TEMPA,5 ;set it again, and 

00BD 1327 00560 bcf TEMPA,6 ;clear the overload LED 

00561 

00BE 0827 00562 Dunb movf TEMPA,W ;move LED data back to PORTB 

00BF 0086 00563 movwf PORTB 

00564 

00C0 01A8 00565 clrf TEMPB 

00C1 03A8 00566 decf TEMPB,F ;set TEMPB to -1 

00567 

00C2 0AA8 00568 NewSetincf TEMPB,F ;count up 

00C3 0CA7 00569 rrf TEMPA,F ;rotate least sig bit INTo carry 

00C4 1C03 00570 btfss STATUS,C ;is carry set now? 

00C5 28C2 00571 goto NewSet ;no, try again 

00572 

00C6 0828 00573 movf TEMPB,W ;yes, put count in w 

00C7 20DD 00574 call Tbl ;get corresponding value for PWM 

00C8 00A4 00575 movwf SETPOINT ;put value in SETPOINT 

00576 

00C9 01A2 00577 Nob clrf DNCL ;clear down button debounce counter 

00CA 01A0 00578 clrf UPCL ;clear up button debounce counter 

00CB 30F9 00579 movlw DEL1 

00CC 00A3 00580 movwf DNCH ;preset down button debounce counter 

00CD 00A1 00581 movwf UPCH ;preset up button debounce counter high byte 

00582 

00583 

;**************************************************************************** 

00584 ;* Wc3 VUNREG has been converted by now, 

00585 ;* Get result, save in VUNREG. 

00586 ;* 

00587 ;* Select VOUT to aquire. 

00588 ;* 

00589 ;* Test VUNREG to see if it has dropped too low. 

00590 ;* If too low, call protective shut-down. 

00591 ;* 


00593 ;* VUNREG Input voltage. 

00594 

;**************************************************************************** 

00595 

00CE 00596 Wc3 

00CE 191F 00597 btfsc ADCON0,GO_DONE ;test if done 

00CF 28CE 00598 goto Wc3 ;no, wait some more 

00D0 081E 00599 movf ADRES,W ;get conversion result 

00D1 00A6 00600 movwf VUNREG ;save result 

00601 

00D2 3089 00602 movlw AVOUT ;select feedback channel to aquire 

00D3 009F 00603 movwf ADCON0 

00604 

00D4 0826 00605 movf VUNREG,W ;get UNREG 

00D5 3C50 00606 sublw 0x50 ;10V-VUNREG=? C=1 if VUNREG


00621 ;* E1H:E1 Previous error 

00622 

;**************************************************************************** 

00623 

00D8 00624 Shift 

00D8 0831 00625 movf E0,W 

00D9 00B3 00626 movwf E1 

00627 

00DA 0832 00628 movf E0H,W 

00DB 00B4 00629 movwf E1H 

00630 

00DC 2836 00631 goto Again 

00632 

00633 

;**************************************************************************** 

00634 ;* Tbl Look up table. 

00635 ;* 

00636 ;* Called with an index in W. 

00637 ;* 

00638 ;* Index is added to program counter. 

00639 ;* 

00640 ;* Execution jumps to "retlw" which will return 

00641 ;* to the calling program with table value in w. 

00642 ;* 


00644 ;* w Offset index into table 

00645 ;* 


00647 ;* w Value from table 

00648 

;**************************************************************************** 

00649 

00DD 00650 Tbl ;call with index in w 

00DD 0782 00651 addwf PCL,F ;add index to PC 

00652 

00DE 344D 3474 3482 00653 dt 0x4d, 0x74, 0x82, 0x9b, 0xc2, 0xea 

349B 34C2 34EA 

00654 ;output voltage 3.0 4.5 5.0 6.0 7.5 9.0 

00655 

00656 

;**************************************************************************** 

00657 ;* ShutDn Protective shutdown. Entry into this routine is a result 

00658 ;* of a low input voltage. This turns off the converter 

00659 ;* before the series pass transistor can overheat. 

00660 ;* 

00661 ;* PWM on-time is set to 0, turning off the converter. 

00662 ;* 

00663 ;* The converter trip LED is lit, indicating shutdown. 

00664 ;* 

00665 ;* Execution then loops without exit. The only exit is to 

00666 ;* reset the controller. 

00667 

;**************************************************************************** 

00668 

00E4 00669 ShutDn 

00E4 1217 00670 bcf CCP1CON,4 ;turn off PWM 

00E5 1297 00671 bcf CCP1CON,5 

00E6 0195 00672 clrf CCPR1L 

00673 

00E7 1786 00674 bsf PORTB,7 ;light trip LED 

00675 

00E8 00676 Dead 

00E8 28E8 00677 goto Dead ;stays here 

00678 

00679 

00680 END 

AN701 


AN701 

MEMORY USAGE MAP (’X’ = Used, ’-’ = Unused) 

0000 : X---XXXXXXXXXXXX XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX 

0040 : XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX 

0080 : XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX 

00C0 : XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX XXXXXXXXX------- ---------------- 

2000 : -------X-------- ---------------- ---------------- ---------------- 

All other memory blocks unused. 

Program Memory Words Used: 230 

Program Memory Words Free: 1818 

Errors : 0 

Warnings : 0 reported, 0 suppressed 

Messages : 0 reported, 7 suppressed 


AN701 


Note the following details of the code protection feature on PICmicro ® MCUs. 

The PICmicro family meets the specifications contained in the Microchip Data Sheet. 

Microchip believes that its family of PICmicro microcontrollers is one of the most secure products of its kind on the market today, 

when used in the intended manner and under normal conditions. 

There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our knowledge, 

require using the PICmicro microcontroller in a manner outside the operating specifications contained in the data sheet. 

The person doing so may be engaged in theft of intellectual property. 

Microchip is willing to work with the customer who is concerned about the integrity of their code. 

Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not 

mean that we are guaranteeing the product as “unbreakable”. 

Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection features of 

our product. 

If you have any further questions about this matter, please contact the local sales office nearest to you. 

Information contained in this publication regarding device 

applications and the like is intended through suggestion only 

and may be superseded by updates. It is your responsibility to 

ensure that your application meets with your specifications. 

No representation or warranty is given and no liability is 

assumed by Microchip Technology Incorporated with respect 

to the accuracy or use of such information, or infringement of 

patents or other intellectual property rights arising from such 

use or otherwise. Use of Microchip’s products as critical components 

in life support systems is not authorized except with 

express written approval by Microchip. No licenses are conveyed, 

implicitly or otherwise, under any intellectual property 

rights. 

© 2002 Microchip Technology Inc. 

Trademarks 

The Microchip name and logo, the Microchip logo, FilterLab, 

KEELOQ, microID, MPLAB, PIC, PICmicro, PICMASTER, 

PICSTART, PRO MATE, SEEVAL and The Embedded Control 

Solutions Company are registered trademarks of Microchip Technology 

Incorporated in the U.S.A. and other countries. 

dsPIC, ECONOMONITOR, FanSense, FlexROM, fuzzyLAB, 

In-Circuit Serial Programming, ICSP, ICEPIC, microPort, 

Migratable Memory, MPASM, MPLIB, MPLINK, MPSIM, 

MXDEV, PICC, PICDEM, PICDEM.net, rfPIC, Select <strong>Mode</strong> 

and Total Endurance are trademarks of Microchip Technology 

Incorporated in the U.S.A. 

Serialized Quick Turn Programming (SQTP) is a service mark 

of Microchip Technology Incorporated in the U.S.A. 

All other trademarks mentioned herein are property of their 

respective companies. 

© 2002, Microchip Technology Incorporated, Printed in the 

U.S.A., All Rights Reserved. 

Printed on recycled paper. 

Microchip received QS-9000 quality system 

certification for its worldwide headquarters, 

design and wafer fabrication facilities in 

Chandler and Tempe, Arizona in July 1999. The 

Company’s quality system processes and 

procedures are QS-9000 compliant for its 

PICmicro ® 8-bit MCUs, KEELOQ ® code hopping 

devices, Serial EEPROMs and microperipheral 

products. In addition, Microchip’s quality 

system for the design and manufacture of 

development systems is ISO 9001 certified.

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Co., Ltd., Chengdu Liaison Office 

Rm. 2401, 24th Floor, 

Ming Xing Financial Tower 

No. 88 TIDU Street 

Chengdu 610016, China 

Tel: 86-28-6766200 Fax: 86-28-6766599 

China - Fuzhou 


Co., Ltd., Fuzhou Liaison Office 

Unit 28F, World Trade Plaza 

No. 71 Wusi Road 

Fuzhou 350001, China 

Tel: 86-591-7503506 Fax: 86-591-7503521 

China - Shanghai 


Co., Ltd. 

Room 701, Bldg. B 

Far East International Plaza 

No. 317 Xian Xia Road 

Shanghai, 200051 

Tel: 86-21-6275-5700 Fax: 86-21-6275-5060 

China - Shenzhen 


Co., Ltd., Shenzhen Liaison Office 

Rm. 1315, 13/F, Shenzhen Kerry Centre, 

Renminnan Lu 

Shenzhen 518001, China 

Tel: 86-755-2350361 Fax: 86-755-2366086 

Hong Kong 

Microchip Technology Hongkong Ltd. 

Unit 901-6, Tower 2, Metroplaza 

223 Hing Fong Road 

Kwai Fong, N.T., Hong Kong 

Tel: 852-2401-1200 Fax: 852-2401-3431 

India 

Microchip Technology Inc. 

India Liaison Office 

Divyasree Chambers 

1 Floor, Wing A (A3/A4) 

No. 11, O’Shaugnessey Road 

Bangalore, 560 025, India 

Tel: 91-80-2290061 Fax: 91-80-2290062 

Japan 

Microchip Technology Japan K.K. 

Benex S-1 6F 

3-18-20, Shinyokohama 

Kohoku-Ku, Yokohama-shi 

Kanagawa, 222-0033, Japan 

Tel: 81-45-471- 6166 Fax: 81-45-471-6122 

Korea 

Microchip Technology Korea 

168-1, Youngbo Bldg. 3 Floor 

Samsung-Dong, Kangnam-Ku 

Seoul, Korea 135-882 

Tel: 82-2-554-7200 Fax: 82-2-558-5934 

Singapore 

Microchip Technology Singapore Pte Ltd. 

200 Middle Road 

#07-02 Prime Centre 

Singapore, 188980 

Tel: 65-334-8870 Fax: 65-334-8850 

Taiwan 

Microchip Technology Taiwan 

11F-3, No. 207 

Tung Hua North Road 

Taipei, 105, Taiwan 

Tel: 886-2-2717-7175 Fax: 886-2-2545-0139 

EUROPE 

Denmark 

Microchip Technology Nordic ApS 

Regus Business Centre 

Lautrup hoj 1-3 

Ballerup DK-2750 Denmark 

Tel: 45 4420 9895 Fax: 45 4420 9910 

France 

Microchip Technology SARL 

Parc d’Activite du Moulin de Massy 

43 Rue du Saule Trapu 

Batiment A - ler Etage 

91300 Massy, France 

Tel: 33-1-69-53-63-20 Fax: 33-1-69-30-90-79 

Germany 

Microchip Technology GmbH 

Gustav-Heinemann Ring 125 

D-81739 Munich, Germany 

Tel: 49-89-627-144 0 Fax: 49-89-627-144-44 

Italy 

Microchip Technology SRL 

Centro Direzionale Colleoni 

Palazzo Taurus 1 V. Le Colleoni 1 

20041 Agrate Brianza 

Milan, Italy 

Tel: 39-039-65791-1 Fax: 39-039-6899883 

United Kingdom 

Arizona Microchip Technology Ltd. 

505 Eskdale Road 

Winnersh Triangle 

Wokingham 

Berkshire, England RG41 5TU 

Tel: 44 118 921 5869 Fax: 44-118 921-5820 

01/18/02 

© 2002 Microchip Technology Inc.

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