Interfaces and Connectors
EBX-22 Reference Manual
57
AND
AL, 01h
;Isolate the BUSY bit
JNZ
BUSY
;Loop back if SPI transaction is not complete
MOV DX,
1D8h
MOV
AL, 27h
;SPICONTROL: SPI Mode 00, 24bit, auto DIO_1_SS#
OUT DX,
AL
MOV DX,
1D9h
MOV
AL, 30h
;SPISTATUS: 8MHz, no IRQ, left-shift
OUT DX,
AL
MOV DX,
1DBh
MOV
AL, 44h
;SPIDATA1: Mirror & Open-Drain interrupts
OUT DX,
AL
MOV DX,
1DCh
MOV
AL, 0Ah
;SPIDATA2: MCP23S17 address 0x0A
OUT DX,
AL
MOV DX,
1DDh
MOV
AL, 40h
;SPIDATA3: MCP23S17 write command
OUT DX,
AL
Writing to a Digital I/O Port Using the SPI Interface
The following code example initiates a write of 55h to Digital I/O port bits DIO15-DIO8.
;Write 44h to configure MCP23S17 register IOCON
MOV
DX,
1D8h
MOV
AL, 26h
;SPICONTROL: SPI Mode 00, 24bit, DIO_0_SS#
OUT
DX,
AL
MOV
DX,
1D9h
MOV
AL, 30h
;SPISTATUS: 8MHz, no IRQ, left-shift
OUT
DX,
AL
MOV
DX,
1DBh
MOV
AL, 44h
;SPIDATA1: mirror and open-drain interrupts
OUT
DX,
AL
MOV
DX,
1DCh
MOV
AL, 0Ah
;SPIDATA2: MCP23S17 IOCON register address 0Ah
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
;Configure MCP23S17 register IODIRA for outputs
MOV
DX,
1DBh
MOV
AL, 00h
;SPIDATA1: 00h for outputs
OUT
DX,
AL
MOV
DX,
1DCh
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
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