Cirrus-logic AN89 Manual de usuario descargar pdf (Pagina 8)

AN89

8 AN89Rev2

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

* Routine - convert

* Input - none

* Output - Conversion results in memory locations HIGHBYTE, MIDBYTE and

* LOWBYTE. This algorithm performs only single conversions. If

* continuous conversions are needed the routine needs to be

* modified. Port flag is zero.

* HIGHBYTE MIDBYTE LOWBYTE

* 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0

* 16-bit results MSB LSB 1 1 1 1 0 0 OD OF

* 20-bit results MSB LSB 0 0 OD OF

* This subroutine initiates a single conversion.

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

convert LDA #$C0 ; Set COMMANDBYTE for single CONV

STA COMMANDBYTE

JSR send_spi ; Transmit command out SPI

LDA #$94 ; Set command byte for config read

STA COMMANDBYTE ; Send COMMAND BYTE

done1 JSR read_register ; Poll done flag until CONV complete

BRCLR 3,LOWBYTE,done1 ; Repeat if Done Flag not Set

LDA #$96 ; Set Byte to Read Conversion Reg.

STA COMMANDBYTE ; Store COMMAND BYTE

JSR read_register ; Acquire the Conversion

RTS ; Exit subroutine

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

* Routine - write_register

* Input - COMMANDBYTE, HIGHBYTE, MIDBYTE, LOWBYTE

* Output - none

* This subroutine instructs the CS5525/6/9 to write to an internal register.

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

write_register LDA COMMANDBYTE ; Load ACCA with COMMANDBYTE

JSR send_spi ; transfer byte

LDA HIGHBYTE ; Load ACCA with HIGHBYTE

JSR send_spi ; transfer byte

LDA MIDBYTE ; Load ACCA with MIDBYTE

JSR send_spi ; transfer byte

LDA LOWBYTE ; Load ACCA with LOWBYTE

JSR send_spi ; transfer byte

RTS ; Exit Subroutine

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Cirrus-logic AN89 Manual de usuario Pagina 8