MCP23S17T-ESO 查看數據表（PDF） - Microchip Technology

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MCP23S17T-ESO

16-Bit I/O Expander with Serial Interface

Microchip Technology 

MCP23017/MCP23S17

3.2.3 SPI INTERFACE

3.2.3.1 SPI Write Operation

The SPI write operation is started by lowering CS. The

Write command (slave address with R/W bit cleared) is

then clocked into the device. The opcode is followed by

an address and at least one data byte.

3.2.3.2 SPI Read Operation

The SPI read operation is started by lowering CS. The

SPI read command (slave address with R/W bit set) is

then clocked into the device. The opcode is followed by

an address, with at least one data byte being clocked

out of the device.

3.2.3.3 SPI Sequential Write/Read

For sequential operations, instead of deselecting the

device by raising CS, the master clocks the next byte

pointed to by the Address Pointer. (see Section 3.2.1

“Byte Mode and Sequential Mode” for details

regarding sequential operation control).

The sequence ends by the raising of CS.

The MCP23S17 Address Pointer will roll over to

address zero after reaching the last register address.

3.3 Hardware Address Decoder

The hardware address pins are used to determine the

device address. To address a device, the correspond-

ing address bits in the control byte must match the pin

state. The pins must be biased externally.

3.3.1

ADDRESSING I2C DEVICES

(MCP23017)

The MCP23017 is a slave I2C interface device that

supports 7-bit slave addressing, with the read/write bit

filling out the control byte. The slave address contains

four fixed bits and three user-defined hardware

address bits (pins A2, A1 and A0). Figure 3-4 shows

the control byte format.

3.3.2

ADDRESSING SPI DEVICES

(MCP23S17)

The MCP23S17 is a slave SPI device. The slave

address contains four fixed bits and three user-defined

hardware address bits (if enabled via IOCON.HAEN)

(pins A2, A1 and A0) with the read/write bit filling out

the control byte. Figure 3-5 shows the control byte

format. The address pins should be externally biased

even if disabled (IOCON.HAEN = 0).

FIGURE 3-4:

I2C CONTROL BYTE

FORMAT

Control Byte

S 0 1 0 0 A2 A1 A0 R/W ACK

Slave Address

Start

bit

R/W = 0 = write

R/W = 1 = read

R/W bit

ACK bit

FIGURE 3-5:

SPI CONTROL BYTE

FORMAT

CS

Control Byte

0 1 0 0 A2 A1 A0 R/W

Slave Address

R/W bit

R/W = 0 = write

R/W = 1 = read

FIGURE 3-6:

I2C ADDRESSING REGISTERS

S 0 1 0 0 A2 A1 A0 0 ACK * A7 A6 A5 A4 A3 A2 A1 A0 ACK *

Device Opcode

R/W = 0

*The ACKs are provided by the MCP23017.

Register Address

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DS20001952C-page 15

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