Cirrus-logic AN131 Bedienungsanleitung PDF herunterladen (Seite 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

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