делал по 2 способу.
Спойлер
title "PIC16f877 sample"list p=16f877
#include <p16f877.inc>
f4l equ 0x20
f4h equ 0x21
f5 equ 0x22
f6l equ 0x23
f6m equ 0x24
f6h equ 0x25
k equ 0x26
org 00h
goto Start
Start
clrf f6h
clrf f6l
clrf f6m
movlw 0x8
movwf k
bcf STATUS,C
m1
rrf f5,1
btfsc STATUS,C
goto m2
goto m3
m2
movf f4l,0
addwf f6l,1
btfsc STATUS,C
goto m4
goto m5
m5
incf f6m
m4
movf f4h,0
addwf f6m,1
btfss STATUS,C
goto m3
goto m6
m6
incf f6h
m3
rlf f4l,1
rlf f4h,1
decf k,1
btfss STATUS,Z
goto m1
nop
end


