MCP23017-ESLASHML datasheet(8/48 Pages) MICROCHIP

8 / 48 page

MCP23017/MCP23S17

DS21952B-page 8

1.4

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.

1.4.1

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 1-2 shows

the control byte format.

1.4.2

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 1-3 shows the control byte

format. The address pins should be externally biased

even if disabled (IOCON.HAEN = 0).

FIGURE 1-2:

I2C™ CONTROL BYTE

FORMAT

FIGURE 1-3:

SPI CONTROL BYTE

FORMAT

FIGURE 1-4:

I2C™ ADDRESSING REGISTERS

FIGURE 1-5:

SPI ADDRESSING REGISTERS

A2A1A0 R/W ACK

Start

bit

Slave Address

R/W bit

ACK bit

Control Byte

R/W = 0 = write

R/W = 1 = read

A2 A1 A0 R/W

Slave Address

R/W bit

Control Byte

R/W = 0 = write

R/W = 1 = read

A2 A1 A0

ACK*

Device Opcode

R/W = 0

*The ACKs are provided by the MCP23017.

100

R/W

A6A5A4A3A2A1A0

Device Opcode

* Address pins are enabled/disabled via IOCON.HAEN.

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