📄 msp430x11x1_tmp100.asm
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;*******************************************************************************
; MSP430x11x1 Demo - Software I2C Master Interface to TMP100
;
; Description: I2C communication with a TMP100, in default condition, is
; demonstrated. If temperature read > 30C (01Eh), P1.0 is set, else reset.
; Only upper 8-bits from TMP100 temperature register are used, representing
; 7Fh = 128C, 80h = -128C. Slave Acknowledge error checking not implemented.
; I2C timing assumed with MCLK ~800kHz.
; ACLK = n/a, MCLK = SMCLK = default DCO ~800kHz
;
; MSP430F1121
; -----------------
; /|\ /|\ /|\| XIN|-
; 10k 10k | | |
; /|\ TMP100 | | --|RST XOUT|-
; | ------- | | | |
; +--|Vcc SDA|<-|---+---->|P2.0 P1.0|---> LED
; +--|A0 | | | |
; -|A1 | | | |
; +--|Vss SCL|<-+---------|P2.1 |
; \|/ ------- | |
;
;
;
; CPU registers used
RXTXI2C .equ R7
ADDRI2C .equ R8
DATAI2C .equ R9
BITI2C .equ R10
;
; Definitions for I2C bus
SDA .equ 001h ; P2.0 controls SDA line (pull-up)
SCL .equ 002h ; P2.1 controls SCL line (pull-up)
Code .equ 09Eh ; Device Code with A0=1, A1=float
;Code .equ 09Ch ; Device Code with A1=A0=1
;
; M. Buccini / Z. Albus
; Texas Instruments Inc.
; May 2005
; Built with Code Composer Essentials Version: 1.0
;*******************************************************************************
.cdecls C,LIST, "msp430x11x1.h"
;-------------------------------------------------------------------------------
.text
;-------------------------------------------------------------------------------
RESET mov.w #300h,SP ; Initialize stackpointer
mov.w #WDTPW+WDTHOLD,&WDTCTL ; Stop WDT
bis.b #01h,&P1DIR ;
;
Mainloop mov.b #0,ADDRI2C ; ADDRI2C = Pointer
call #Read_I2C ;
bic.b #01h,&P1OUT ; P1.0 = 0
cmp.b #01Eh,DATAI2C ; DATAI2C > 30c?
jlo Mainloop ; Again
bis.b #01h,&P1OUT ; P1.0 = 1
jmp Mainloop ; Again
;
;;/////////I2C Subroutines start//////////////////////////////////////////////
;-------------------------------------------------------------------------------
Read_I2C; enter ADDRI2C=00 - FF I2C device address to read
; RXTXI2C=x
; DATAI2C=x
; exit ADDRI2C=x
; RXTXI2C=x
; DATAI2C=00 - FF I2C device data
;-------------------------------------------------------------------------------
mov.b #Code,RXTXI2C ; Control
call #I2C_Start ; Send Start, control and Ack
mov.b ADDRI2C,RXTXI2C ; Address
call #I2C_TX ; Send address and Ack
mov.b #Code,RXTXI2C ; Control
bis.b #01h,RXTXI2C ; "read"
call #I2C_Start ; Send Start, control+1 and Ack
call #I2C_RX ; Send Read
call #I2C_RX_NAck ; Send NAck
call #I2C_Stop ; Send Stop
ret ;
;
;-------------------------------------------------------------------------------
I2C_Start; enter SDA=x, SCL=x
; exit SDA=1, SCL=0
;-------------------------------------------------------------------------------
bic.b #SCL+SDA,&P2DIR ; SCL and SDA to input direction
bic.b #SCL+SDA,&P2OUT ; SCL=1, SDA=1
bis.b #SDA,&P2DIR ; SDA=0
bis.b #SCL,&P2DIR ; SCL=0
;-------------------------------------------------------------------------------
I2C_TX; enter SDA=1, SCL=0
; exit SDA=1, SCL=0
;-------------------------------------------------------------------------------
mov #8,BITI2C ;
I2C_TX_Bit rla.b RXTXI2C ; data bit -> carry
jc I2C_TX1 ;
I2C_TX0 bis.b #SDA,&P2DIR ; SDA=0
jmp I2C_TXx ;
I2C_TX1 bic.b #SDA,&P2DIR ; SDA=1
I2C_TXx bic.b #SCL,&P2DIR ; SCL=1
nop ; delay to meet I2C spec
nop ;
bis.b #SCL,&P2DIR ; SCL=0
dec BITI2C ;
jnz I2C_TX_Bit ; continue until 8 bits are sent
bic.b #SDA,&P2DIR ; SDA=1
;
I2C_TX_Ack bic.b #SCL,&P2DIR ; SCL=1
; bit.b #SDA,&P2IN ; Slave_Ack --> carry
; jnc I2C_Error ; No carry = Ack error
nop ; delay to meet I2C spec
nop ;
bis.b #SCL,&P2DIR ; SCL=0
ret ; Return from subroutine
;
;-------------------------------------------------------------------------------
I2C_RX ; enter SDA=1, SCL=0
; exit SDA=1, SCL=0
;-------------------------------------------------------------------------------
mov.b #8,BITI2C ; 8 bits to read
I2C_RX_Bit bic.b #SCL,&P2DIR ; SCL=1
bit.b #SDA,&P2IN ; SDA bit -> carry
rlc.b DATAI2C ; store data bit
bis.b #SCL,&P2DIR ; SCL=0
dec BITI2C ; all bits read?
jnz I2C_RX_Bit ; continue until 8 bits are read
ret ; Return from subroutine
;
I2C_RX_Ack bis.b #SDA,&P2DIR ; SDA=0, Master Ack
I2C_RX_NAck bic.b #SCL,&P2DIR ; SCL=1
nop ; delay to meet I2C spec
nop ;
bis.b #SCL,&P2DIR ; SCL=0
bic.b #SDA,&P2DIR ; SDA=1
ret ; Return from subroutine
;
;-------------------------------------------------------------------------------
I2C_Stop; enter SDA=x, SCL=0
; exit SDA=1, SCL=1
;-------------------------------------------------------------------------------
bis.b #SDA,&P2DIR ; SDA = 0
bic.b #SCL,&P2DIR ; SCL = 1
bic.b #SDA,&P2DIR ; SDA = 1
I2C_End ret ;
;
;-------------------------------------------------------------------------------
; Interrupt Vectors
;-------------------------------------------------------------------------------
.sect ".reset" ; MSP430 RESET Vector
.short RESET ;
.end
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