VersaLogic VL-EBX-37, Reference Manual

Page: 43 / 71

Interfaces and Connectors
EBX-37 Reference Manual
37
;Configure MCP23S17 register IODIRA for outputs
MOV DX, CABh
MOV AL, 00h ;SPIDATA1: 00h for outputs
OUT DX, AL
MOV DX, CACh
MOV AL, 00h ;SPIDATA2: MCP23S17 register address 00h
OUT DX, AL
MOV DX, CADh
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, CABh
MOV AL, 55h ;SPIDATA1: data to write
OUT DX, AL
MOV DX, CACh
MOV AL, 14h ;SPIDATA2: MCP23S17 register address 14h
OUT DX, AL
MOV DX, CADh
MOV AL, 40h ;SPIDATA3: MCP23S17 write command
OUT DX, AL
CALL BUSY ;Poll busy flag to wait for SPI transaction
BUSY: MOV
DX, CA9h
IN AL, DX ;Get SPISTATUS
AND AL, 01h ;Isolate the BUSY flag
JNZ BUSY ;Loop if SPI transaction not complete