User guide

AN89

AN89Rev2 7

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* Subroutines

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* Routine - initialize

* Input - none

* Output - none

* This subroutine initializes port D for interfacing to the CS5525/6/9 ADC.

* It provides a time delay for oscillator start-up/wake-up period.

* A typical start-up time for a 32768 Hz crystal, due to high Q, is 500 ms.

* Also 1003 XIN clock cycles are allotted for the ADC’s power on reset.

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initialize LDA #%01010000 ; Load ACCA with for SPSC

STA SPCR ; Setup SPI

LDA #40 ; Load ACCA with delay count

JSR delay ; Delay, Power on Reset 1003 XIN

LDA #220 ; Load ACCA with delay count

JSR delay ; Delay, Oscillator start-up 170 mS

LDX #$0F ; Reset Serial Port on ADC

LDA #$FF ; Load ACCA with $FF

loop JSR send_spi ; Move $FF to SPDR

DECX ; Decrement the counter

BNE loop ; Repeat loop is counter not zero

LDA #%11111110 ; Load ACCA with last byte

JSR send_spi ; Move $FE to SPDR

RTS ; Exit subroutine

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* Routine - calibrate

* Input - none

* Output - none

* This subroutine instructs the CS5525/6/9 to perform self-calibration.

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calibrate LDA #$84 ; set command byte for config write

STA COMMANDBYTE ; set COMMAND BYTE

CLR HIGHBYTE ; clear HIGHBYTE

CLR MIDBYTE ; clear MIDBYTE

LDA #$01 ; get ready for self offset cal

STA LOWBYTE ; set LOWBYTE

JSR write_register ; Write to Config Register

LDA #$94 ; set command byte for config read

STA COMMANDBYTE ; set COMMAND BYTE

poll_done: JSR read_register ; Poll done flag until cal complete

BRCLR 3,LOWBYTE,poll_done; repeat if flag not set

RTS ; Exit subroutine