Datasheet

MAX7318
generates the acknowledge bit since the MAX7318 is
the recipient. When the MAX7318 is transmitting to the
master, the master generates the acknowledge bit.
Slave Address
The MAX7318 has a 7-bit-long slave address (Figure 6).
The 8th bit following the 7-bit slave address is the R/W
bit. Set this bit low for a write command and high for a
read command.
Slave address pins AD2, AD1, and AD0 choose 1 of 64
slave ID addresses (Table 7).
Data Bus Transaction
The command byte is the first byte to follow the 8-bit
device slave address during a write transmission
(Table 1, Figure 7). The command byte is used to deter-
mine which of the following registers are written or read.
Writing to Port Registers
Transmit data to the MAX7318 by sending the device
slave address and setting the LSB to a logic zero. The
command byte is sent after the address and deter-
mines which registers receive the data following the
command byte (Figure 7).
2-Wire-Interfaced, 16-Bit, I/O Port Expander
with Interrupt and Hot-Insertion Protection
8 _______________________________________________________________________________________
SDA
SDA
A6 A5 A4 A3 A2 A1 A0
MSB LSB
ACKR/W
PROGRAMMABLE
Figure 6. Slave Address
COMMAND BYTE
ADDRESS (hex)
FUNCTION PROTOCOL
POWER-UP
DEFAULT
0x00 Input port 1 Read byte XXXX XXXX
0x01 Input port 2 Read byte XXXX XXXX
0x02 Output port 1 Read/write byte 1111 1111
0x03 Output port 2 Read/write byte 1111 1111
0x04 Port 1 polarity inversion Read/write byte 0000 0000
0x05 Port 2 polarity inversion Read/write byte 0000 0000
0x06 Port 1 configuration Read/write byte 1111 1111
0x07 Port 2 configuration Read/write byte 1111 1111
0xFF Factory reserved. (Do not write to this register.) — —
Table 1. Command-Byte Register
123456789
SCL
SDA
S A0000001 76543210A76543210A0A
SLAVE ADDRESS
COMMAND BYTE PORT 1 DATA PORT 2 DATA
R/W
ACKNOWLEDGE
FROM SLAVE
ACKNOWLEDGE
FROM SLAVE
START
CONDITION
ACKNOWLEDGE
FROM SLAVE
ACKNOWLEDGE
FROM SLAVE
t
PV
t
PV
WRITE TO PORT
DATA OUT PORT 1
READ FROM PORT 2
Figure 7. Writes to Output Registers Through Write-Byte Protocol