i2cslave.asm

ADI公司

;======================================================================
;
; Author        : ADI - Apps              www.analog.com/MicroConverter
;
; Date          : May 2002
;
; File          : i2cslave.asm
;
; Hardware      : ADuC814
;
; Description   : Code for a slave 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

BYTECNT         DATA    30h       ; byte counter for I2C routines
INPUT           DATA    31h       ; data recieved from master
OUTPUT          DATA    32h       ; data to be transmitted to master

GO              BIT     00h       ; flag to wait for interrupts
FIRST           BIT     01h       ; flag to indicate first receive Int

LED             EQU     P3.4      ; P3.4 drives the LED on eval board

;____________________________________________________________________
                                                  ; BEGINNING OF CODE
CSEG
ORG 0000h
        JMP MAIN
;____________________________________________________________________
                                                           ; INT0 ISR
ORG 0003h
        INC     OUTPUT
        RETI
;____________________________________________________________________
                                                            ; I2C ISR
ORG 003Bh  

      JB      I2CTX, SLAVE_TRANSMITTER

SLAVE_RECEIVER:
      JB      FIRST, ENDINT1  ; if first INT then wait for next int
      SETB    GO              ; reception complete 
      MOV     INPUT, I2CDAT   ; store data received in INPUT
      JMP     ENDINT1

SLAVE_TRANSMITTER:
      SETB    GO              ; transmission complete
      MOV     I2CDAT, OUTPUT  ; move data to be transmitted into I2CDAT
      JMP     ENDINT2         ; Note: On the ADuC824/816 the read or
                              ;       write of I2CDAT register 
                              ;       automatically clears i2ci. If
                              ;       I2CI is cleared twice then the
                              ;       microconverter will hang.)

ENDINT1:
      CLR     I2CI            ; clear I2C interrupt bit (812 only)
ENDINT2:
      CLR     FIRST           ; address has already been received
      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

; configure pins for 812s
      MOV     CFG814,#01H

;configure and enable interrupts
;      MOV     IE2,#01h       ; enable I2C interrupt
      MOV     IEIP2,#01h    ; enable I2C interrupt
      SETB    EX0            ; enable INT0
      SETB    IT0            ; INT0 edge triggered
      SETB    EA             ; allow all the interrupts

;initialize settings
      MOV     I2CADD,#044h   ; slave address is 44h
      MOV     I2CCON,#00h    ; slave mode (default=>not necessary)
      CLR     GO             ; clear flag to wait for interrupt
                             ; GO is set once data is TX'd or RX'd
      SETB    FIRST          ; FIRST is cleared after receiving the
                             ; first SLAVE receiver interrupt

      MOV     OUTPUT,#0      ; first byte to be transmitted is 40h 
      CLR     LED

WAITFORDATA:  
      JNB     GO,$           ; ----- wait for i2c interrupt ------
                             ; If it is in receive mode, it will 
                             ; wait here for a second interrupt (as 
                             ; the first interrupt only contains the
                             ; slave address in I2CDAT).
                             ; In transmit mode the tranmission will
                             ; occur after the first interrupt.
      SETB    FIRST          ; re-initialise flags
      CLR     GO
      JB      I2CTX,WAITFORDATA
                             ; if the slave has just transmitted then
                             ; wait to receive a byte 
                             ; if the slave has just received then
                             ; send input up the UART
  	
SENDUART:
      CPL     LED            ; LED changes each time one byte has been 
                             ; received and another transmitted

      MOV     A,INPUT        ; send value received out the UART
      CALL    SENDVAL
      MOV     A,#10
      CALL    SENDCHAR       ; send LF + CR
      MOV     A,#13
      CALL    SENDCHAR

      JNB     RI, WAITFORDATA      ; repeat (unless UART data received)

; WHEN UART DATA RECEIVED, MOVE DATA TO I2C OUTPUT...

      MOV     OUTPUT, SBUF    ; update OUTPUT byte to new value
      CLR     RI              ; must clear RI
      JMP     WAITFORDATA     ; back to main loop


;======================================================================
;                             SUBROUTINES
;======================================================================

;____________________________________________________________________
                                                           ; 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