Rainbow Electronics MAX7311 - Manual (Page 8)

MAX7311
MAX7311 generates the acknowledge bit since the
MAX7311 is the recipient. When the MAX7311 is trans-
mitting to the master, the master generates the
acknowledge bit.
Slave Address
The MAX7311 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 MAX7311 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
8 _______________________________________________________________________________________
SDA
SDA
A6 A5 A4 A3 A2 A1 A0
MSB LSB
ACK R/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
0x08 Timeout register Read/write byte 0000 0001
0xFF Factory reserved. (Do not write to this register.) — —
Table 1. Command Byte Register
1 2 3 4 5 6 7 8 9 SCL
SDA S A 0 0 0 0 0 0 1 7 6 5 4 3 2 1 0 A 7 6 5 4 3 2 1 0 A 0 A 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