VersaLogic SPX-2, Reference Manual

Page: 14 / 17

Digital I/O
SPX Reference Manual
10
MOV AL, 00h ;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
;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 14h
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