Slave data should increment from 0x00 with each transmitted byte ; which is verified by the Master.. ; LED off for address or data Ack; LED on for address or data NAck.
Trang 1; MSP430G2x21/G2x31 Demo - I2C Master Receiver, single byte
;
; Description: I2C Master communicates with I2C Slave using
; the USI Slave data should increment from 0x00 with each transmitted byte
; which is verified by the Master
; LED off for address or data Ack; LED on for address or data NAck
; ACLK = n/a, MCLK = SMCLK = Calibrated 1MHz
;
; ***THIS IS THE MASTER CODE***
;
; Slave Master
; (msp430g2x21_usi_09.asm)
; MSP430G2x21/G2x31 MSP430G2x21/G2x31
;
-; /|\| /|\|
XIN|-; | | | | | |
; |RST |RST
XOUT|-; | | | |
; LED <-|P1.0 | | |
; | | | P1.0|-> LED
; | SDA/P1.7| ->|P1.7/SDA |
; | SCL/P1.6|< -|P1.6/SCL |
;
; Note: internal pull-ups are used in this example for SDA & SCL
;
; D Dang
; Texas Instruments Inc
; October 2010
; Built with Code Composer Essentials Version: 4.2.0
;****************************************************************************** I2CState .equ R4
slav_data .equ R5
slav_add .equ R6
cdecls C,LIST, "msp430g2221.h"
.text ; Program Start
; -RESET mov.w #0280h,SP ; Initialize stackpointer
StopWDT mov.w #WDTPW+WDTHOLD,&WDTCTL ; Stop watchdog timer
CheckCal cmp.b #0FFh,&CALBC1_1MHZ ; Calibration constants erased? jeq Trap
cmp.b #0FFh,&CALDCO_1MHZ
jne Load
Trap jmp $ ; Trap CPU!!
Load mov.b &CALBC1_1MHZ,&BCSCTL1 ; Set DCO to 1MHz
mov.b &CALDCO_1MHZ,&DCOCTL
SetupP1 mov.b #0xC0,&P1OUT ; P1.6&P1.7 Pullups
bis.b #0xC0,&P1REN ; P1.6&P1.7 Pullups
mov.b #0xFF,&P1DIR ; unused pins as output
SetupP2 clr.b &P2OUT
mov.b #0xFF,&P2DIR
SetupUSI mov.b #USIPE6+USIPE7+USIMST+USISWRST,&USICTL0; Port, I2C master mov.b #USIIE+USII2C,&USICTL1 ; Enable I2C
mov.b #USIDIV_3+USISSEL_2+USICKPL,&USICKCTL ; SMCLK/8
bis.b #USIIFGCC,&USICNT ; Disable automatic clear control bic.b #USISWRST,&USICTL0 ; Enable USI
bic.b #USIIFG,&USICTL1 ; Clear pending flag
clr.w I2CState
clr.b slav_data
mov.b #0x91,slav_add
Trang 2Mainloop bis.b #USIIFG,&USICTL1
bis.w #LPM0+GIE,SR ; Enter LPM0, enable interrupts call #Delay
jmp Mainloop
; -USI_ISR ;
add.w I2CState,PC ; I2C State Machine
jmp STATE0
jmp STATE2
jmp STATE4
jmp STATE6
jmp STATE8
jmp STATE10
STATE0
bis.b #0x01,&P1OUT ; LED on: sequence start
clr.b &USISRL ; Generate start condition
bis.b #USIGE+USIOE,&USICTL0 ;
bic.b #USIGE,&USICTL0 ; & send address to slave
mov.b slav_add,&USISRL ; and transmit address R/W =1
mov.b &USICNT,R8 ; Bit counter = 8, Tx adress
and.b #0xE0,R8
add.b #0x08,R8
mov.b R8,&USICNT
mov.w #2,I2CState ; Go to next state rx address (N)ACK bic.b #USIIFG,&USICTL1 ; clear pending flag
reti
STATE2 ; Rx address (N)Ack bit bic.b #USIOE,&USICTL0 ; SDA = input
bis.b #0x01,&USICNT ; Bit counter = 1, rx (N)ACK
mov.w #4,I2CState ; Go to next state, chk (N)ACK
bic.b #USIIFG,&USICTL1
reti
STATE4 ; Process Address (N)ack, data Rx bit.b #0x01,&USISRL ; if NACK received
jnc Data_Rx ;
bis.b #USIOE,&USICTL0 ;
clr.b &USISRL
bis.b #0x01,&USICNT ; bit counter = 1, SCL high,SDA low mov.w #10,I2CState ; go to next state, generate stop bis.b #0x01,&P1OUT ; Turn on LED : error
bic.b #USIIFG,&USICTL1
reti
Data_Rx
bis.b #8,&USICNT ; bit counter = 8, Rx data
mov.w #6,I2CState ; next state: Test data, (N)ACK bic.b #0x1,&P1OUT ; LED off
bic.b #USIIFG,&USICTL1
reti
STATE6 ; Send Data (N)Ack bit
bis.b #USIOE,&USICTL0 ; SDA = output
cmp.b slav_data,&USISRL ; if data valid
jnz Data_NACK ; data invalid , goto NACK loop clr.b &USISRL ; send ACK
inc.b slav_data ; Increment slave data
bic.b #0x01,&P1OUT ; LED off
jmp STATE6_Exit
Data_NACK
mov.b #0xFF,&USISRL ; Send NACK
bis.b #0x1,&P1OUT ; LED on:error
Trang 3STATE6_Exit
bis.b #0x1,&USICNT ; Bit counter = 1, send NACK bit mov.w #8,I2CState ; go to next state, prep stop
bic.b #USIIFG,&USICTL1
reti
STATE8 ; Pre stop condition
bis.b #USIOE,&USICTL0 ; SDA =output
clr.b &USISRL
bis.b #0x01,&USICNT ; Bit counter = 1, SCL high,SDA low mov.w #10,I2CState ; go to next state, generate stop bic.b #USIIFG,&USICTL1
reti
STATE10
mov.b #0xFF,&USISRL ; USISRL=1 to release SDA
bis.b #USIGE,&USICTL0 ; Transparent latch enabled
bic.b #USIGE+USIOE,&USICTL0 ; Latch/SDA output disabled
clr.w I2CState ; Reset state machine for next Tx bic.w #LPM0,0(SP) ; Exit active for next transfer bic.b #USIIFG,&USICTL1
reti
; -Delay
mov.w #0xFFFF,R7 ; Delay betn communication cycles DL1 dec.w R7
jnz DL1
ret
; -; Interrupt Vectors
.sect ".reset" ; MSP430 RESET Vector
short RESET ;
sect ".int04" ; USI Vector
short USI_ISR ;
end