📄 i2cmstr.asm
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;======================================================================
;
; Author : ADI - Apps www.analog.com/MicroConverter
;
; Date : May 2002
;
; File : i2Cmstr.asm
;
; Hardware : ADuC814
;
; Description : Code for a master in an I2C system. This code will
; continuously receive and transmit a byte over the I2C
; interface, then send the received byte out the UART,
; then check if a character had been entered in the UART,
; if so, it will send the ASCII value of the character
; entered to the slave, the next time it transmits a byte.
;
; Reference : Tech Note, uC001: "MicroConverter I2C Compatible
; Interface" find it at www.analog.com/microconverter
;
;======================================================================
$MOD814
;____________________________________________________________________
; DEFINE VARIABLES IN INTERNAL RAM
BITCNT DATA 30h ; bit counter for I2C routines
SLAVEADD DATA 31h ; slave address for I2C routines
INPUT DATA 32h ; data recieved from the slave
OUTPUT DATA 33h ; data to be transmitted to slave
NOACK BIT 00h ; I2C no acknowledge flag
ERR BIT 00h ; I2C error flag
LED EQU P3.4
;____________________________________________________________________
; BEGINNING OF CODE
CSEG
ORG 0000h
JMP MAIN
;____________________________________________________________________
; INT0 ISR
ORG 0003h
INC OUTPUT
RETI
;____________________________________________________________________
; MAIN PROGRAM
ORG 0060h
MAIN:
; configure the UART ADuC812s
MOV RCAP2H,#0FFh ; config UART for 9830baud
MOV RCAP2L,#-7 ; (close enough to 9600baud)
MOV TH2,#0FFh
MOV TL2,#-7
MOV SCON,#52h
MOV T2CON,#34h
; enable i2c pins on 812s
MOV CFG814,#01H
; configure & enable interrupts
SETB EX0 ; enable INT0
SETB IT0 ; INT0 edge triggered
SETB EA ; allow all the interrupts
; initialise settings
MOV SLAVEADD,#88H ; clear RW bit
MOV I2CCON,#0A8h ; sets SDATA & SCLOCK, and
; selects master mode
MOV OUTPUT,#0 ; TX 0 as default
CLR NOACK
CLR ERR
RXTXLOOP:
; code for a read mode ( master recieves one byte from slave )
CALL RCVDATA ; sends start bit
; sends address byte
; checks acknowledge
; receives byte into ACC
; checks ACK
; sends stop bit
; code for write mode ( master transmits one byte to slave )
CALL SENDDATA ; sends start bit
; sends address byte
; checks acknowledge
; transmits ACC
; checks ACK
; sends stop bit
; Check for Error message
JB ERR,SENDERR ; if error, send error message
; Transmit received byte (INPUT) up UART to PC (hyperterminal)
MOV A,INPUT ; put value received into ACC
CALL SENDVAL ; send value received out the UART
JMP SKIP
SENDERR:
CALL ERROR ; send error message out the UART
CLR ERR ; clear error flag
SKIP:
MOV A,#10 ; send LF+CR
CALL SENDCHAR
MOV A,#13
CALL SENDCHAR
; Toggle LED (1s delay so that LED can be seen toggle)
MOV A, #10
CALL DELAY
CPL LED
; Check for new OUTPUT
JNB RI, RXTXLOOP ; repeat (unless UART data received)
; If UART data received, then save to OUTPUT
MOV OUTPUT,SBUF ; update OUTPUT byte to new value
CLR RI ; must clear RI
JMP RXTXLOOP ; back to main loop
;====================================================================
; SUBROUTINES
;====================================================================
;____________________________________________________________________
; SENDDATA
; Send all the sequence to the slave (slave address + data (OUTPUT))
SENDDATA:
; send start bit
CALL STARTBIT ; acquire bus and send slave address
; send slave address
MOV A, SLAVEADD
CALL SENDBYTE ; sets NOACK if NACK received
JB NOACK, STOPSEND ; if no acknowledge send stop
; send OUTPUT byte
MOV A, OUTPUT
CALL SENDBYTE ; sets NOACK if NACK received
STOPSEND:
CALL STOPBIT ; sends stop bit
JNB NOACK, SENDRET ; if slave sends NACK send error
SETB ERR ; sets the error flag
SENDRET:
RET
;____________________________________________________________________
; RCVDATA
; receives one or more bytes of data from an I2C slave device.
RCVDATA:
INC SLAVEADD ; Set RW for reception
; send start bit
CALL STARTBIT ; acquire bus and send slave address
; send slave address
MOV A, SLAVEADD
CALL SENDBYTE ; sets NOACK if NACK received
DEC SLAVEADD ; returns SLAVEADD to 88h (after INC)
JB NOACK, STOPRCV ; Check for slave not responding.
CALL RCVBYTE ; Receive next data byte.
MOV INPUT,A ; Save data byte in buffer.
STOPRCV:
CALL STOPBIT
JNB NOACK, RCVRET ; if slave sends NACK send error
SETB ERR ; sets the error flag
RCVRET:
RET
;____________________________________________________________________
; STARTBIT
; Sends the start bit to initiate an I2C communication
STARTBIT:
SETB MDE ; enable SDATA pin as an output
CLR NOACK
CLR MDO ; low O/P on SDATA
CLR MCO ; start bit
RET
;____________________________________________________________________
; STOPBIT
; Sends the stop bit to end an I2C transmission
STOPBIT:
SETB MDE ; to enable SDATA pin as an output
CLR MDO ; get SDATA ready for stop
SETB MCO ; set clock for stop
SETB MDO ; this is the stop bit
RET
;____________________________________________________________________
; SENDBYTE
; Send 8-bits in ACC to the slave
SENDBYTE:
MOV BITCNT,#8 ; 8 bits in a byte
SETB MDE ; to enable SDATA pin as an output
CLR MCO ; make sure that the clock line is low
SENDBIT:
RLC A ; put data bit to be sent into carry
MOV MDO,C ; put data bit on SDATA line
SETB MCO ; clock to send bit
CLR MCO ; clear clock
DJNZ BITCNT,SENDBIT ; jump back and send all eight bits
CLR MDE ; release data line for acknowledge
SETB MCO ; send clock for acknowledge
JNB MDI,NEXT ; this is a check for acknowledge
SETB NOACK ; no acknowledge, set flag
NEXT: CLR MCO ; clear clock
RET
;____________________________________________________________________
; RCVBYTE
; receives one byte of data from an I2C slave device. Returns it in A
RCVBYTE:
MOV BITCNT,#8 ; Set bit count.
CLR MDE ; to enable SDATA pin as an input
CLR MCO ; make sure the clock line is low
RCVBIT:
SETB MCO ; clock to recieve bit
CLR MCO ; clear clock
MOV C,MDI ; read data bit into carry.
RLC A ; Rotate bit into result byte.
DJNZ BITCNT,RCVBIT ; Repeat until all bits received.
; recieved byte is in the accumulator
SETB MDE ; Data pin =Output for NACK
SETB MDO ; Send NACK (always send NACK for
; last byte in transmission)
SETB MCO ; Send NACK clock.
CLR MCO
RET
;____________________________________________________________________
; DELAY
; DELAY ROUTINE FOR THE ADuC812/ADuC816/ADuC824
DELAY: ; Delays by 100ms * A
; ADuC812 100ms based on 11.0592MHz Core Clock
; ADuC824 100ms based on 1.573MHz Core Clock
MOV R2,A ; Acc holds delay variable
;DLY0: MOV R3,#200 ; Set up delay loop0
;DLY1: MOV R4,#229 ; Set up delay loop1
DLY0: MOV R3,#22H ; Set up delay loop0
DLY1: MOV R4,#0FFH ; Set up delay loop1
DJNZ R4,$ ; Dec R4 & Jump here until R4 is 0
; wait here for 131*15.3us=2ms
DJNZ R3,DLY1 ; Dec R3 & Jump DLY1 until R3 is 0
; Wait for 50*2ms
DJNZ R2,DLY0 ; Dec R2 & Jump DLY0 until R2 is 0
; wait for ACC*100ms
RET ; Return from subroutine
;____________________________________________________________________
; ERROR
; this subroutine is run if a NACK is received from the slave
ERROR:
MOV A,#45h
CALL SENDCHAR ; send the letter E out the UART
RET
;____________________________________________________________________
; SENDCHAR
; sends ASCII value contained in A to UART
SENDCHAR:
JNB TI,$ ; wait til present char gone
CLR TI ; must clear TI
MOV SBUF,A
RET
;____________________________________________________________________
; HEX2ASCII
; converts A into the hex character representing the value of A's
; least significant nibble
HEX2ASCII:
ANL A,#00Fh
CJNE A,#00Ah,$+3
JC IO0030
ADD A,#007h
IO0030: ADD A,#'0'
RET
;____________________________________________________________________
; SENDVAL
; converts the hex value of A into two ASCII chars, and then spits
; these two characters up the UART. does not change the value of A.
SENDVAL:
PUSH ACC
SWAP A
CALL HEX2ASCII
CALL SENDCHAR ; send high nibble
POP ACC
PUSH ACC
CALL HEX2ASCII
CALL SENDCHAR ; send low nibble
POP ACC
RET
;____________________________________________________________________
END
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