;******************************************************************************
;   MSP-FET430P140 Demo - I2C, Slave Reads/Writes to MSP430 Master
;
;  Description: This example shows the repeated start condition  It talks to
;  the MSP430F169.  It first does two writes, then sends repeated start and
;  does a read, then sets STP.
;  Access ready Interrupt occurs when 2 bytes are sent by master, and then
;  master is switched to Reciever. Another ARDY Interrupt occurs when data
;  is read from I2CDRB and then a stop condition is issued.
;  The received data is in R6 and is checked for validity. If the received
;  data is incorrect, the CPU is trapped and P1.0 LED will stay on.
;
;  This is the Slave code.
;  The Master code is called fet140_i2c_11.s43
;
;  ACLK = n/a, MCLK = SMCLK = I2CCLOCK = DCO ~ 800kHz
;  //* MSP430F15x, MSP430F16x Device Required *//
;
;                                 /|\  /|\
;                  MSP430F169     10k  10k     MSP430F169
;                    slave         |    |        master
;              -----------------|  |    |  -----------------
;             |             P3.1|<-|---+->|P3.1             |
;             |                 |  |      |             P1.0|-->LED
;             |                 |  |      |                 |
;             |             P3.3|<-+----->|P3.3             |
;             |                 |         |                 |
;
;
;   H. Grewal / L. Westlund
;   Texas Instruments Inc.
;   Nov 2005
;   Built with IAR Embedded Workbench Version: 3.30A
;******************************************************************************
#include  <msp430x16x.h>
;------------------------------------------------------------------------------
            ORG     01100h                  ; Progam Start
;------------------------------------------------------------------------------
RESET       mov.w   #0A00h,SP               ; Initialize stackpointer
StopWDT     mov.w   #WDTPW+WDTHOLD,&WDTCTL  ; Stop WDT
            bis.b   #0Ah,&P3SEL             ; Select I2C pins
            bis.b   #01h,&P1DIR             ; P1.0 output
            bic.b   #01h,&P1OUT             ; Clear P1.0

I2C_init    bis.b   #I2C+SYNC,&U0CTL        ; Recommended init procedure
            bic.b   #I2CEN,&U0CTL           ; Recommended init procedure
            bis.b   #I2CSSEL1,&I2CTCTL      ; SMCLK
            mov.w   #0048h,&I2COA           ; Own Address is 048h
            bis.b   #TXRDYIE+RXRDYIE,&I2CIE ; Enable TXRDYIFG,RXRDYIFG interrupt
            bis.b   #I2CEN,&U0CTL           ; Enable I2C

            clr.w   R5                      ; Use R5 to hold TX data
            clr.w   R6                      ; Use R6 to hold RX data
            clr.w   R7                      ; use R7 to check received data
Mainloop    bis.b   #LPM0+GIE,SR            ; Enter LPM0, enable interrupts
            bic.b   #TXRDYIE+RXRDYIE,&I2CIE ; Disable TXRDYIFG,RXRDYIFG interrupt
            bis.b   #01h,&P1OUT             ; Set P1.0
            jmp     $                       ; Trap CPU

;------------------------------------------------------------------------------
I2C_ISR;    Common ISR for I2C Module
;------------------------------------------------------------------------------
            add.w  &I2CIV,PC               ; Add I2C offset vector
            reti                            ; No Interrupt
            reti                            ; Arbitration lost
            reti                            ; No Acknowledge
            reti                            ; Own Address
            reti                            ; Register Access Ready
            jmp     RXRDY_ISR               ; Receive Ready
            jmp     TXRDY_ISR               ; Transmit Ready
            reti                            ; General Call
            reti                            ; Start Condition

RXRDY_ISR   mov.b   &I2CDRB,R6              ; RX data in R5
            cmp.w   R6,R7                   ; Test received data
            jne     Trap                    ; Trap CPU if wrong
            inc.b   R7                      ; Increment correct RX value
            jmp     returnint
Trap        bic.w   #LPM0,0(SP)             ; Clear LPM0
returnint   reti

TXRDY_ISR   mov.b   R5,&I2CDRB              ; Load I2CDRB
            inc.b   R5                      ; Increment data
            reti

;------------------------------------------------------------------------------
;           Interrupt Vectors
;------------------------------------------------------------------------------
            ORG     0FFFEh                  ; MSP430 RESET vector
            DW      RESET                   ;
            ORG     0FFF0h                  ; I2C interrupt vector
            DW      I2C_ISR
            END