This document contains assembly code for a PIC16F887 microcontroller to emulate a heart rate monitor and smart power socket. It includes code for different states like ready, datalog, and end. It uses timers, ADC, interrupts and other PIC16F887 features. Subroutines are used for debouncing buttons, delays and blinking LEDs. The code shows how assembly programming allows direct hardware access for embedded applications.

1. Contents Page
1B-i: Heart Monitor 1
1B-ii: Smart Socket 5
Appendix-i: Subroutines 9
Appendix-ii: Assembly
Code (1B-i)
10
Appendix-iii: Assembly
Code (1B-ii)
14
H63ECH - Embedded Computing
(AUT 15 -16)
Coursework 1B
PIC16F887 Assembly Programming
Submitted By:
Osama Azim (ID: 023799),
M.Sc. Electronics Communication and Computer
Engineering

2. Coursework - 1B : PIC16F887 Assembly Programming
1 | H63ECH - Embedded Computing Osama Azim
1B-i : Heart Monitor
o Introduction:
With available on-board I/O's on the PIC Kit2 - one push button, eight LEDs - the
coursework objectives resemble a simplified heart beat monitor.
Following prominent features of a portable heart beat recorder/monitor were required to be
developed on a PIC16F887 Microcontroller (MCU) in PIC Assembly language using the
MPLAB assembler:
 User identification stored in device memory and displayed - emulated by storing
Student ID in MCU EEPROM and successful write operation indicated on LEDs
 Device ready or in standby mode - emulated by signaling an LED on/off
 Data-logging of heart beat sensor readings - emulated by blinking an LED
intermittently
 End of data-log - emulated by indicating appropriate LED sequence upon input from
a pushbutton
o State Diagram and Flow Charts:
Above described coursework objectives can be represented by following state diagram:
State actions:
State Ready: LED 0 is turned ON, initially device enters State Ready by a pushbutton press after EEPROM
data writing.
State Datalog: LED 0 maintained ON while LED 1 blinks intermittently, next transition is upon a
double click of pushbutton and further delay of 3 seconds. LED 4 turned on to indicate a
double press and hold on time.
State End: LED 0, LED 1 are turned OFF, LED 2 turned ON. Transition back to State Ready
on Button press.
Figure1: State diagram
State
Ready
State
DataLog
ButtonPress
= 0
ButtonPress = 1
Double Press = 1,
Delay 3 sec.
Button Double
Press = 0
State
End
ButtonPress = 1
ButtonPress
= 0

3. Main Program Flow Chart
No
No
No
Write Student ID to EEPROM
Start
Debounce
Button
Press?
Turn On LED 5,6,7 :
from Port D
Debounce
State Ready:
LED 0 ON,
LED 2 OFF
Button
Press?
State Datalog:
LED 1 OFF
Delay
Decrement ENDATAL
ENDDATAL
= 1?
State End:
LED-2 ON,
LED-0 OFF,
LED-1 OFF,
LED-4 OFF
LED 1 ON
Button
Press?
Delay
Yes
Yes
Double Click
Double
Click?
Load "10"
To ENDDATAL
Yes
Yes
No
No
Yes

4. Coursework - 1B : PIC16F887 Assembly Programming
3 | H63ECH - Embedded Computing Osama Azim
Flow Chart for Double Click:
Notes on double click:
 Hold time for continuous button press during LED 1 blink cycle can be adjusted by
loading appropriate value to DINTERVAL (for max press time) register.
 Second click wait time can also be adjusted similarly by loading an appropriate value
to DINTERVAL after first click release
Yes
From
Main
Program
Flow
Yes
Load DINTERVAL
(For maximum second click
wait time)
No
DINTERVAL
= 0 ?
No
Load DINTERVAL
(For maximum press time)
Timer
Button
Press?
Decrement
DINTERVAL
State Datalog:
Blink Routine
Button
Press?
Yes
No
Timer
Button
Press?
Load ENDDATAL,
LED-4 ON
Yes
Decrement
DINTERVAL
DINTERVAL
= 0 ?
No
Yes
No

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o Discussion and Conclusion:
All coursework objectives were realized with certain modifications and known issues, these
are noted in following points:
 A debounce subroutine was developed to filter out unwanted, noise like, pushbutton
transitions during button press. This subroutine, although effective, was not
extensively optimized and a more efficient debounce logic can be developed.
 The transition hold time of 3 seconds from State DataLog to State End is indicated by
LED 4 being turned ON, this also indicates a successful double press. Though not
essential, this feature was implemented for a better device state indication - as the
double click can often be disregarded due to exit from second click hold time or short
successive click interval.
 Upon detecting a click in between of State Datalog blink loop, LED 1 is maintained
ON until a second click is detected or maximum wait time for second click is reached,
whichever occurs earlier. The program developed could not check for double click
while blinking LED 1 simultaneously, but the LED 1 hold ON time during double click
subroutine can be reduced by adjusting the wait time for second click.
Conclusion and Learning outcome:
 Programming with a lower level language, assembly, is directly dependent on the
target CPU/MCU. This is in contrast with higher level languages like C - for which the
compiler provides an illusion of codes being generic for multiple machine
architectures.
 Considering that every CPU/MCU is designed with their respective assembly
instructions, programs written in assembly for a specific architecture is more robust
when compared to a higher level language.
 Due to its hardware dependent nature, optimum hardware utilization can be
achieved by programming in assembly. This is especially useful for embedded
applications, wherein a CPU/MCU is dedicated to execute predetermined tasks,
keeping cost of hardware down along with achieving a higher degree of reliability.

6. Coursework - 1B : PIC16F887 Assembly Programming
5 | H63ECH - Embedded Computing Osama Azim
1B-ii : Smart Power Socket
Introduction:
As described in the Coursework-1A report, the Smart Power Socket was conceptualized as an IoT device
with IP based remote switching and monitoring.
The features realized using the provided PIC16F887 MCU based PIC Kit 2 development board:
 A Button Press emulates the remote command to switch device On/Off. With an initial press of
pushbutton, appropriate LED is turned On or Off.
 Current consumed by appliance is emulated by varying the voltage supplied to MCU ADC
through the onboard potentiometer.
Usage of ADC :
The PIC16F887 ADC is configured with following parameters:
 Port: PORT A, PIN 0
 Channel: RA 0 - ADC channel 0
 ADC voltage reference: Positive: Vdd, Negative: Vss
 ADC conversion clock: Fosc/8
 Result Formatting: Left Justified
The conversion process is executed in following steps:
Figure 1: ADC conversion TAD Cycles
The output result format used is left justified, the ADRESH register that holds the conversion result has
following structure:

7. Coursework - 1B : PIC16F887 Assembly Programming
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Figure 2: ADRESH register format
The ADC conversion result is calculated using the formula:
ADC = VIN/VREF * 1023
The application designed for this coursework turns ON a respective LED in accordance to the voltage
level converted at the ADC. The PIC Kit 2 development board has 8 LEDs connected to PORT D.
Considering an input voltage range of 0V to 5V, each LED is stepped on a voltage of 0.625V (5V/8). The
reference ADRESH value to stitch LEDs is calculated below:
LED ON
Voltage In
(v)
ADC Value Binary
Decimal Ref
(ADRESH)
0 0.625 128 00100000 00 32
1 1.25 255 00111111 11 63
2 1.875 384 01100000 00 96
3 2.5 512 10000000 00 128
4 3.125 640 10100000 00 160
5 3.75 767 10111111 11 191
6 4.37 894 11011111 10 223
7 ~5 1019 11111110 11 254
o State Diagram and Flow Chart:
The program toggles between two states as explained below:
State OFF: All LEDs turned OFF, wait for push button to transition to State ON.
State ON: Capture ADC value and turn ON respective LED to signify voltage level. Next press
of Pushbutton makes the transition back to State OFF.
Figure1: State diagram
State
OFF
ButtonPress
= 0
State
ON
ButtonPress = 1
ButtonPress
= 0
ButtonPress = 1

8. Coursework - 1B : PIC16F887 Assembly Programming
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Flow Chart for Smart Plug:
Start
Move
ADRESH to W
Yes
Delay Cycle
for Capacitor
Start A2D
Conversion
A2D
Done?
Debounce
Button
Press?
Yes
No
No
Button
Press?
Yes
Clear PORT D -
All LEDs Off
No
YesADRESH =
"x" Volt Level?
No "x" matching
LED = ON
Clear
PORT D

9. Coursework - 1B : PIC16F887 Assembly Programming
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o Discussion and Conclusion:
Known Issues:
 After successive On/Off transitions, the LEDs were found not to turn on by press of
pushbutton, and would turn on only after a change in potentiometer value.
Design Limitations and Conclusion:
Achieving complex design objectives, such as IoT based control, through Assembly is a
lengthy process which would require extensive effort - these objectives can be achieved
with relative ease through higher level programming languages. The focus of this
coursework was not to implement a feature heavy design, but to understand the various
machine level operations such as calculated usage of ADC or utilization of MCU timers, for
example.
Assembly programming, as its uniquely defined for each device, enables complete hardware
usage of target CPU/MCU - this allows for an in depth understanding of the various
computing and peripheral components that make up a MCU. Although assembly codes are
not suitable for real world applications today, knowledge of the underlying hardware and
understanding of the "assembly program development approach" would encourage
programmers to develop efficient programs in higher level languages as well.

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Appendix - i : Subroutines
Subroutines used at multiple instances in Coursework:
COUNTD:
B7 B6 B5 B4 B3 B2 B1 B0
x x x x x x x 1/0
Appropriate COUNTD bit can be tested for required delay to achieve debounce
Flow Chart for
Timer Subroutine:
Using:
Overflow time = 4 * (1/Fosc) *
Prescale * (256-TMR 0)
We have:
Overflow Time = 6.55 x 10-2
sec
Flow Chart for
Delay subroutine:
Delay = (6.55 x 10-2
Sec) * (2X
)
Flow Chart for
Debounce Subroutine:
Yes
Timer
Timer
Rolled
Over?
No
Clear Interrupt
Flag
RETURN
No
Delay "x" ms
TIME1
=0?
RETURN
Yes
Move Time
Multiplier to
TIME1
Timer
Decrement
Time Multiplier
Moved to BUTTOND, and B0
tested for denounced Press
Move COUNTD
to BUTTOND
Yes
Debounce
Button
Press?
No
Delay
Increment
COUNTD
Button
Release?
No
Yes
Delay
Clear COUNTD
RETURN

11. Coursework - 1B : PIC16F887 Assembly Programming
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Appendix - ii : Coursework 1B-i , Heart Beat Monitor, Assembly Code
#include <p16F887.inc>
__CONFIG _CONFIG1, _LVP_OFF & _FCMEN_OFF & _IESO_OFF & _BOR_OFF &
_CPD_OFF & _CP_OFF & _MCLRE_OFF & _PWRTE_ON & _WDT_OFF & _INTRC_OSC_NOCLKOUT
__CONFIG _CONFIG2, _WRT_OFF & _BOR21V
cblock 0x20
COUNTD
BUTTOND
TCOUNT
TIME
TIME1
COUNTER
DINTERVAL
ENDDATAL
endc
org 0
START: BSF STATUS, RP0 ;SELECT BANK 1
MOVLW B'00000111' ; CONFIGURE TIMER0 PRESCALER BITS
MOVWF OPTION_REG ; MOVE TO OPTION REG
MOVLW 0x01
MOVWF TRISB ; PORTB, PIN0 SET AS INPUT FOR SWITCH
CLRF TRISD ; PORTD SET TO ALL OUTPUTS FOR LEDs
BSF STATUS, RP1 ; SELECT REGISTER BANK 3
MOVLW 0X00
MOVWF ANSELH ; PORTB PINS SET AS DIGITAL INPUT
BCF STATUS, RP0 ; SELECT REGISTER BANK 0
BCF STATUS, RP1
CLRF PORTD ; INITIALIZE PORTD AS ALL OFF (LEDs)
CLRF COUNTD ; CLEAR GPR DATA
CLRF BUTTOND
CLRF COUNTER
CLRF TCOUNT
CLRF TIME
CLRF ENDDATAL

12. Coursework - 1B : PIC16F887 Assembly Programming
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BSF STATUS, RP1 ; SELECT BANK 2
MOVLW D'99' ; DECIMAL 99, LAST DIGITS OF STUDENT ID:023799
MOVWF EEDATA ; LOAD TO EEDATA
MOVLW 0x20 ; EEPROM ADDRESS
MOVWF EEADR
BSF STATUS, RP0 ; SELECT BANK 3
BSF EECON1, 2 ; WRITE ENABLE FOR EEPROM
BCF INTCON, 7 ; DISABLE GLOBAL INTERRUPTS
MOVLW 0x55 ; SAFETY PROCEDURE
MOVWF EECON2
MOVLW 0xAA
MOVWF EECON2
BSF EECON1, 1 ; START WRITING
BCF STATUS, RP0 ; SELECT BANK 0
BCF STATUS, RP1
BSF PORTD, 5 ; LED 5, 6, 7 ON TO INDICATE WRITE COMPLETE
BSF PORTD, 6
BSF PORTD, 7
S_READY: CALL DEBOUNCE1 ; CHECK DEBOUNCE, BUTTON PRESS
BTFSS BUTTOND, 0 ; BUTTON PRESS?
GOTO S_READY
BSF PORTD, 0 ; INDICATE STATE READY
BCF PORTD, 2 ; CLEAR INDICATION FOR STATE END
S_DATALOG: CALL DEBOUNCE1 ; CHECK DEBOUNCE, BUTTON PRESS
BTFSS BUTTOND, 0 ; BUTTON PRESS?
GOTO S_DATALOG
BLINK: BCF PORTD, 1 ; START BLINK, LED 1 = OFF
CALL DELAY260 ; LED 1 OFF DELAY
DECF ENDDATAL ; CHECK IF DATALOG STATE NEEDS TO END,
;DECREMENT ENDDATAL REGISTER
MOVF ENDDATAL, W ; CHECK IF ENDDATAL HAS REACHED 1
XORLW 1
BTFSC STATUS, Z ; IF YES, GOTO STATE END
GOTO S_END
BSF PORTD, 1 ; BLINK, LED 1 = ON
CALL DELAY260 ; LED 1 ON DELAY
BTFSC PORTB, 0 ; CHECK IF BUTTON IS PRESSED
GOTO BLINK ; IF NOT, LOOP BLINK

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GOTO DOUBLEC ; IF YES, CHECK FOR DOUBLE CLICK
S_END: CLRF ENDDATAL ; CLEAR ENDDATAL REGISTER
BSF PORTD, 2 ; INDIACATE STATE END BY LED 2 = ON
BCF PORTD, 0 ; TURN OFF OTHER LEDs
BCF PORTD, 1
BCF PORTD, 4
CALL DELAY1000
GOTO S_READY ; GO TO STATE READY, CHEC FOR NEXT
; BUTTON PRESS
DEBOUNCE1: BTFSC PORTB, 0 ; CHECK IF BUTTON PRESSED
GOTO DEBOUNCE1
CALL DELAY130 ; DELAY TO FILTER FALSE CLICKS
CLRW
INCF COUNTD ; INCREMENT DEBOUNCE COUNTS, TO
; B'00000001'
BTFSS PORTB, 0 ; CHECK IF BUTTON RELEASED
GOTO $-1
CALL DELAY130 ; DELAY TO FILTER FALSE RELEASE
MOVF COUNTD,W ; MOVE DEBOUNCE COUNT TO BITTOND. BUTTOND
; IS NOW B'00000001'
MOVWF BUTTOND
CLRF COUNTD ; CLEAR COUNTD REGISTER
RETURN ; RETURN FROM DEBOUNCE
DOUBLEC: MOVLW D'3' ; LOAD MAXIMUM PRESS DELAY TO DINTERVAL
MOVWF DINTERVAL
CALL DELAY520
BTFSC PORTB, 0 ; BUTTON STILL PRESSED?
GOTO CHECK ; IF NOT, CHECK FOR SECOND PRESS
DECR1: CALL TIMER ; DECREMENT MAXIMUM PRESS COUNT
DECFSZ DINTERVAL
GOTO DECR1
GOTO BLINK ; RETURN TO BLINK
CHECK: MOVLW D'32' ; LOAD MAXIMUM WAIT FOR SECOND PRESS TO
DINTERVAL
MOVWF DINTERVAL
CALL TIMER
CHECK2: BTFSC PORTB, 0 ; CHECK FOR SECOND PRESS
GOTO DECR2 ; WAIT FOR SECOND PRESS
MOVLW D'10' ; LOAD ENDDATAL WITH BLINK END DELAY TIME
MOVWF ENDDATAL
BSF PORTD, 4 ; INDICATE DOUBLE PRESS WITH LED 4 = ON
GOTO BLINK

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DECR2: CALL TIMER ; DECREMENT DINTERVAL FOR SECOND PRESS WAIT
DECFSZ DINTERVAL
GOTO CHECK2
GOTO BLINK ; RETURN TO BLINK IF NO SECOND PRESS
TIMER: BTFSS INTCON, T0IF ; WAIT FOR TIMER TO ROLL OVER
GOTO TIMER
BCF INTCON, T0IF ; CLEAR INTERRUPT FLAG
RETURN
DELAY130: MOVLW D'1' ; LOAD TIME MULTIPLYER TO TIME1
MOVWF TIME1
CALL TIMER
DECFSZ TIME1,F ; DECREMENT TIME1, RETURN IF ZERO
GOTO $-2
RETURN
DELAY260: MOVLW D'3'
MOVWF TIME1
CALL TIMER
DECFSZ TIME1,F
GOTO $-2
RETURN
DELAY520: MOVLW D'7'
MOVWF TIME1
CALL TIMER
DECFSZ TIME1,F
GOTO $-2
RETURN
DELAY1000: MOVLW D'15'
MOVWF TIME1
CALL TIMER
DECFSZ TIME1,F
GOTO $-2
RETURN
DELAY2000: MOVLW D'31'
MOVWF TIME1
CALL TIMER
DECFSZ TIME1,F
GOTO $-2
RETURN
END

15. Coursework - 1B : PIC16F887 Assembly Programming
14 | H63ECH - Embedded Computing Osama Azim
Appendix - iii : Coursework 1B-ii , Smart Power Socket, Assembly Code
#include <p16F887.inc>
__CONFIG _CONFIG1, _LVP_OFF & _FCMEN_OFF & _IESO_OFF & _BOR_OFF &
_CPD_OFF & _CP_OFF & _MCLRE_OFF & _PWRTE_ON & _WDT_OFF & _INTRC_OSC_NOCLKOUT
__CONFIG _CONFIG2, _WRT_OFF & _BOR21V
cblock 0x20
COUNTD
BUTTOND
TIME
TIME1
DINTERVAL
endc
org 0
START: BSF STATUS,RP0 ; SELECT BANK 1
MOVLW B'00000111'
MOVWF OPTION_REG
MOVLW 0x01
MOVWF TRISB ; PORTB, PIN0 SET AS INPUT FOR SWITCH
MOVLW 0xFF
MOVWF TRISA ; PORT A IS ALL INPUT
CLRF TRISD ; PORT D IS ALL OUTPUT
MOVLW 0x00 ; Left Justified, Vdd-Vss referenced
MOVWF ADCON1
BSF STATUS,RP1 ; SELECT BANK 3
MOVLW 0x01 ; PORT A, PIN0 IS ANALOG
MOVWF ANSEL
MOVLW 0x00 ; PORT B, ALL PINS DIGITAL
MOVWF ANSELH
BCF STATUS,RP0 ; RETURN TO BANK 0
BCF STATUS,RP1
MOVLW 0X41
MOVWF ADCON0 ; A2D CLOCK SET TO Fosc/8, A2D CHANNEL 0
; SELECTED (RA0), TURN ON A2D MODULE

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CLRF ADRESH ; CLEAR/INITIALIZE REGISTERS
CLRF PORTD
CLRF TIME
CLRF TIME1
ON: CLRF PORTD
CALL DEBOUNCE1 ; CHECK DEBOUNCE, BUTTON PRESS
BTFSS BUTTOND,0 ; IF BUTTON PRESSED, GO TO CONVERT A2D
AND TURN LED ON
GOTO ON
ADC: NOP ; WAIT FOR BYPASS CAP TO SETTLE VOLTAGE
NOP
NOP
NOP
NOP
NOP
BSF ADCON0,GO_DONE ; START A2D CONVERSION
BTFSS ADCON0,GO_DONE ; CHECK IF CONVERSION DONE
GOTO $-1
MOVF ADRESH, W ; MOVE CONVERTED VALUE TO W
CN: XORLW 1 ; CHECK IF A2D CONVERSION IS 1, LESS THAN 0.625V
BTFSC STATUS, Z
GOTO LEDN ; RESET PORT D
C0: XORLW 32 ; CHECK IF A2D CONVERSION IS 32, 0.625V
BTFSC STATUS, Z
GOTO LED0 ; LED0 ON
C1: XORLW 63 ; CHECK IF A2D CONVERSION IS 63, 1.25V
BTFSC STATUS, Z
GOTO LED1 ; LED1 ON
C2: XORLW 96 ; CHECK IF A2D CONVERSION IS 96, 1.875V
BTFSC STATUS, Z
GOTO LED2 ; LED2 ON
C3: XORLW 128 ; CHECK IF A2D CONVERSION IS 128, 2.5V
BTFSC STATUS, Z
GOTO LED3 ; LED3 ON
C4: XORLW 160 ; CHECK IF A2D CONVERSION IS 160, 3.125V
BTFSC STATUS, Z
GOTO LED4 ; LED4 ON
C5: XORLW 191 ; CHECK IF A2D CONVERSION IS 191, 3.75V
BTFSC STATUS, Z

17. Coursework - 1B : PIC16F887 Assembly Programming
16 | H63ECH - Embedded Computing Osama Azim
GOTO LED5 ; LED5 ON
C6: XORLW 223 ; CHECK IF A2D CONVERSION IS 223, 4.37V
BTFSC STATUS, Z
GOTO LED6 ; LED6 ON
C7: XORLW 254 ; CHECK IF A2D CONVERSION IS 254, 5V
BTFSC STATUS, Z
GOTO LED7 ; LED7 ON
OFF: BTFSC PORTB,0 ; BUTTON PRESSED?
GOTO ADC ; GOTO CONVERTING A2D IF BUTTON NOT PRESSED
GOTO ON ; GOTO RESET PORT D AND WAIT FOR NEXT BUTTON PRESS
LEDN: CLRF PORTD
GOTO ADC
LED0: CLRF PORTD ; RESET PREVIOUS PORTD D VALUE, LED
BSF PORTD, 0 ; SET APPROPRIATE LED
GOTO ADC ; GOTO CONVERTING A2D
LED1: CLRF PORTD
BSF PORTD, 1
GOTO ADC
LED2: CLRF PORTD
BSF PORTD, 2
GOTO ADC
LED3: CLRF PORTD
BSF PORTD, 3
GOTO ADC
LED4: CLRF PORTD
BSF PORTD, 4
GOTO ADC
LED5: CLRF PORTD
BSF PORTD, 5
GOTO ADC
LED6: CLRF PORTD
BSF PORTD, 6
GOTO ADC
LED7: CLRF PORTD
BSF PORTD, 7
GOTO ADC
DEBOUNCE1: BTFSC PORTB, 0 ; CHECK IF BUTTON PRESSED
GOTO DEBOUNCE1

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CALL DELAY130 ; DELAY TO FILTER FALSE CLICKS
CLRW
INCF COUNTD ; INCREMENT DEBOUNCE COUNTS, TO
;B'00000001'
BTFSS PORTB, 0 ; CHECK IF BUTTON RELEASED
GOTO $-1
CALL DELAY130 ; DELAY TO FILTER FALSE RELEASE
MOVF COUNTD,W ; MOVE DEBOUNCE COUNT TO BITTOND. BUTTOND
;IS NOW B'00000001'
MOVWF BUTTOND
CLRF COUNTD ; CLEAR COUNTD REGISTER
RETURN ; RETURN FROM DEBOUNCE
TIMER: BTFSS INTCON, T0IF
GOTO TIMER
BCF INTCON, T0IF
RETURN
DELAY130: MOVLW D'1'
MOVWF TIME1
CALL TIMER
DECFSZ TIME1,F
GOTO $-2
RETURN
END