Cirrus-logic AN89 Bedienungsanleitung PDF herunterladen (Seite 9)

AN89

AN89Rev2 9

**************************************************************************************

* Routine - read_register

* Input - COMMANDBYTE

* Output - HIGHBYTE, MIDBYTE, LOWBYTE

* This subroutine reads an internal register of the ADC.

**************************************************************************************

read_register LDA COMMANDBYTE ; Load ACCA with COMMANDBYTE

JSR send_spi ; transfer byte

JSR receive_spi ; receive byte

STA HIGHBYTE ; Move ACCA with HIGHBYTE

JSR receive_spi ; receive byte

STA MIDBYTE ; Move ACCA with MIDBYTE

JSR receive_spi ; receive byte

STA LOWBYTE ; Move ACCA with LOWBYTE

RTS ; Exit Subroutine

**************************************************************************************

* Routine - send_spi

* Input - Byte to be transmitted is placed in ACCA

* Output - none

* This subroutine sends a byte to the ADC.

**************************************************************************************

send_spi: STA SPDR ; Move ACCA to SPDR

wait0 BRCLR SPIF,SPSR,wait0 ; Loop until byte is transmitted

RTS ; Exit Subroutine

**************************************************************************************

* Routine - receive_spi

* Input - none

* Output - Byte received is placed in ACCA

* This subroutine receives a byte from the ADC.

**************************************************************************************

receive_spi: CLRA ; Load ACCA register with Zero

STA SPDR ; Initiate a transfer of all Zero’s

wait1 BRCLR SPIF,SPSR,wait1 ; Reset Flag SPIF bit

LDA SPDR ; Move SPDR to ACCA

RTS ; Exit Subroutine

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Cirrus-logic AN89 Bedienungsanleitung Seite 9