Interfaces and Connectors
EBX-11 Reference manual
54
MOV
DX, 1DDh
MOV
AL, 40h
;SPIDATA3: MCP23S17 write command
OUT
DX, AL
CALL BUSY
;Poll busy flag to wait for SPI transaction
;Write 55h to MCP23S17 register GPIOA
MOV
DX, 1DBh
MOV
AL, 55h
;SPIDATA1: data to write
OUT
DX, AL
MOV
DX, 1DCh
MOV
AL, 14h
;SPIDATA2: MCP23S17 register address 00h
OUT
DX, AL
MOV
DX, 1DDh
MOV
AL, 40h
;SPIDATA3: MCP23S17 write command
OUT
DX, AL
CALL BUSY
;Poll busy flag to wait for SPI transaction
BUSY: MOV DX, 1D9h
IN
AL, DX
;Get SPISTATUS
AND
AL, 01h
;Isolate the BUSY flag
JNZ
BUSY
;Loop if SPI transaction not complete
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