Motorola MCU 68HC912 Bedienungsanleitung PDF herunterladen (Seite 8)

SLAA108A

8 SPI-Based Data Acquisition/Monitor Using the TLC2551 Serial ADC

Write_DAC bis.b #001h,&P3OUT ; Turn on LED of F149 Board

swpb R12 ; Swap Bytes

add.w R12, R13

and.w #0xFFF0, R12 ; Strip trailing bits

rrc.w R12 ; Shift data 4 places

rrc.w R12 ; to conform to

rrc.w R12 ; DAC input format

rrc.w R12 ; Data is shifted!

and.w #0x0FFF, R12 ; Strip any carries

add.w #0x4000, R12 ; Set DAC Fast Mode, 0x4000

bic.b #FS,&P3OUT ; Clear FS to DAC

bic.b #DAC_CS,&P3OUT ; Enable /CS to DAC

bis.b #FS,&P3OUT ; Toggle FS to prepare DAC

bic.b #FS,&P3OUT ; to recieve DATA

swpb R12 ; Align MSB First

mov.b R12,&U0TXBUF ; Transmit upper Data Byte to DAC

call #CLEAR

swpb R12 ; Prepare Lower Byte

mov.b R12,&U0TXBUF ; Transmit lower Data Byte to DAC

call #CLEAR

bis.b #DAC_CS,&P3OUT ; Disable /CS to DAC

bis.b #FS,&P3OUT ; Set Frame Sync

bic.b #001h,&P3OUT ; Turn off LED of F149 Board

jmp Mainloop ; Repeat

;*******************************

; Clear TX Flag

;*******************************

CLEAR

bit.b # UTXIFG0,&IFG1; TXBUF ready?

jnc CLEAR ; 1 = ready

bic.b # UTXIFG0,&IFG1

ret

;************************************************************************

Init_Sys; Modules and Controls Registers set-up subroutine

;************************************************************************

StopWDT mov #WDTPW+WDTHOLD,&WDTCTL ; Stop Watchdog Timer

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Motorola MCU 68HC912 Bedienungsanleitung Seite 8