Cirrus Logic AN131 - Manual (Page 10)

AN131
10 AN131REV2
;*****************************************************************************
;* Routine - convert
;* Input - none
;* Output - conversion results in memory locations HIGHBYTE, MIDBYTE and
;*
LOWBYTE. This algorithm performs single conversions on
;* Setup 1. See the CS5521/22/23/24/28 data sheet for multiple
;* conversions or conversions on other channels.
;* This subroutine performs a Single conversion using Setup 1
;*****************************************************************************
convert LDA #$0B ;Command to read Configuration Register
STA COMMAND ;Prepare COMMAND byte
JSR read_register;Read Config. Register
LDA HIGHBYTE ;Get High Byte in ACCA
AND #$F8 ;Mask MC, LP and RC bits to 0
STA HIGHBYTE ;Put info back into High Byte location
LDA #$03 ;Command to write back to config Register
STA COMMAND ;Prepare Command Byte
JSR write_register;Write Configuration Register
;*** Receive Conversion Data ***
LDA #$80 ;Command to convert on Setup 1
JSR send_spi ;Send Command to ADC
poll_sdo2: BRSET 2,PORTD,poll_sdo2 ;Wait for SDO to fall
LDA #$00 ;Load A with all 0’s
JSR send_spi ;Send all 0’s to ADC
JSR receive_spi ;Get high conversion byte
STA HIGHBYTE ;Move info to High Byte location
JSR receive_spi ;Get middle conversion byte
STA MIDBYTE ;Move info to Middle Byte location
JSR receive_spi ;Get low conversion byte
STA LOWBYTE ;Move info to Low Byte location
RTS ;Return
;*****************************************************************************
;* Routine - write_register
;* Input - COMMAND, HIGHBYTE, MIDBYTE, LOWBYTE
;* Output - none
;* This subroutine is used to write information to the internal registers of
;* the CS5521/22/23/24/28
;*****************************************************************************
write_register LDA COMMAND ;Load ACCA with COMMAND
JSR send_spi ;Transfer command byte
LDA HIGHBYTE ;Load ACCA with HIGHBYTE
JSR send_spi ;Transfer high byte
LDA MIDBYTE ;Load ACCA with MIDBYTE
JSR send_spi ;Transfer middle byte
LDA LOWBYTE ;Load ACCA with LOWBYTE