Cirrus-logic AN131 Manual do Utilizador descarregar pdf (Página 8)

AN131

8 AN131REV2

BNE sloop ;Repeat loop if counter isn’t zero

LDA #%11111110 ;Load ACCA with last byte

JSR send_spi ;Send final byte to ADC

RTS ;Exit routine

;*****************************************************************************

;* Routine - write_csrs

;* Input - none

;* Output - none

;* This subroutine is used to write to the Channel Setup Registers. It first

;* changes the depth pointer bits in the configuration register to reflect

;* the number of CSRs to be written, and then writes information to the

;* appropriate number of CSRs.

;*****************************************************************************

write_csrs LDA #$0B ;Command to read config. register

STA COMMAND ;Prepare command byte

JSR read_register;Read the configuration register

;*** Mask DP3-DP0 to access two CSRS (four Setups) ***

LDA MIDBYTE ;Get Middle Byte in ACCA

AND #$3F ;Mask DP3-DP2 low

ORA #$30 ;Mask DP1-DP0 high

STA MIDBYTE ;Put info back into Middle Byte location

LDA #$03 ;Command to write back to config Register

STA COMMAND ;Prepare Command Byte

JSR write_register;Write Configuration Register

;*** Write to CSRs - note, the ADC expects information for the number of

; CSRs indicated in the Depth Bits (DP3-DP0 in the configuration

; register) so all of the CSRs must be written at this time.

LDA #$05 ;Command to write CSRs

JSR send_spi ;send command to ADC

;*** Setup CSR #1 - Setups 1 and 2

; Sets both Setups to a default value of ’000’

; (A1-A0 = 00, Physical Channel = 1, OWR = 15Hz,

; Input V-range = 100mV, Bipolar Measurement Mode)

LDA #$00 ;Load ACCA with zeros

JSR send_spi ;One byte of zero...

JSR send_spi ;Two bytes of zero...

JSR send_spi ;Three bytes of zero.

;*** Setup CSR #2 - Setups 3 and 4

; Sets Setup 3 to ’4C0’ and Setup 4 to ’105’

; Setup 3 Settings - (A1-A0 = 01, Physical Channel = 2, OWR = 101.1Hz,

; input V-range = 100mV, Bipolar)

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Cirrus-logic AN131 Manual do Utilizador Página 8

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