Datasheet

MCP23018/MCP23S18

1.3.2.2 I

C Read Operation

C read operations include the control byte sequence,

as shown in the bottom of Figure 1-1. This sequence is

followed by another control byte (including the Start

condition and ACK) with the R/W bit equal to a logic

one (R/W = 1). The MCP23018 then transmits the data

contained in the addressed register. The sequence is

ended with the master generating a Stop or Restart

condition.

1.3.2.3 I

C Sequential Write/Read

For sequential operations (Write or Read), instead of

transmitting a Stop or Restart condition after the data

transfer, the master clocks the next byte pointed to by

the address pointer (see Section 1.3.1 “Byte Mode

and Sequential Mode” for details regarding sequential

operation control).

The sequence ends with the master sending a Stop or

Restart condition.

The MCP23018 address pointer will roll over to

address zero after reaching the last register address.

Refer to Figure 1-1.

1.3.3 SPI INTERFACE

1.3.3.1 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.

1.3.3.2 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.

1.3.3.3 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 1.3.1

“Byte Mode and Sequential Mode” for details regard-

ing sequential operation control).

The sequence ends by the raising of CS

The MCP23S18 address pointer will roll over to

address zero after reaching the last register address.