Hi friends this is part of the code that handles communication;This Program Written for AT89c51 mProcessor
;to Record & Playback Audio As Interfaced
;with isd4004 sound chip on SPI protocol


$mod51
$print
$noprint

SPCR DATA 0D5H ;SPI CONTROL REGISTER
SPSR DATA 0AAH ;SPI STATUS REGISTER
SPIF EQU 10000000b ;INTERRUPT FLAG
SPDR DATA 86H ;SPI DATA REGISTER

CS EQU P1.4 ;SLAVE SELECT
MOSI EQU P1.5 ;SPI
MISO EQU P1.6 ;SPI
SCK EQU P1.7 ;SPI

rec_button equ p0.0
rec_led equ p2.7
play_button equ p0.1
play_led equ p2.6
stop_button equ p0.2
stop_led equ p2.5

RDSR equ 05h ;read status register
WRSR equ 01h ;write status register
READ equ 03h ;read data from slave
WRITE equ 02h ;write data to slave
WREN equ 06h ;write enable
WRIDI equ 04h ;write disable

A8 bit acc.3 ;msb of address
NRDY bit acc.0 ;high=write cycle in progress






org 0000h


setup:
setb cs
setb mosi
setb miso
setb sck
mov spcr,#55h
setb Play_button
setb rec_button
setb stop_button
setb rec_led
setb play_led
setb stop_led
clr a
jmp operations

operations:

lcall check1
lcall check2
lcall check3
lcall check4
sjmp operations



check1:
jnb play_button,playm

ret
check2:
jnb rec_button,recordm

ret
check3:
jnb stop_button,stopm
ret

RECORDm:
clr rec_led
setb play_led
setb stop_led
clr cs
mov a,#powerup
rrc a
call write_byte
call delay
mov a,#setrec
rrc a
call write_byte
call delay
mov a,#rec
rrc a
call write_byte
call delay
setb cs
setb rec_button
clr a
ret

Playm:
setb rec_led
clr play_led
setb stop_led
clr cs
mov a,#powerup
rrc a
call write_byte
call delay
mov a,#setplay
rrc a
call write_byte
call delay
mov a,#play
rrc a
call write_byte
call delay
setb cs
setb play_button
clr a
ret


stopm:

setb rec_led
setb play_led
clr stop_led
clr cs
mov a,#stop
rrc a
call write_byte
call delay
setb cs
setb stop_button
clr a
ret


write_byte:

clr cs
push acc
mov a,dph
rrc a
mov a,#write
mov a8,c
call masterio
mov a,dpl
call masterio
pop acc
call masterio
setb cs
ret




masterio:
mov spdr,a ;write output data
ret



check4:
cpl P2.2
ret

;4004 control code
powerup: db '00100111'
setplay: db '11100111'
play: db '11110111'
setrec: db '10100111'
rec: db '10110111'
setmic: db '11101000'
mc: db '11111111'
stop: db '01110111'
stoppwrdn: db '01011111'
rint: db '01110111'

end