MAX7300 Maxim, MAX7300 Datasheet - Page 8

• Manufacturer Part Number: MAX7300
• Description: The MAX7300 compact, serial-interfaced, I/O expansion peripheral provides microprocessors with up to 28 ports
• Manufacturer: Maxim

2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or
28-Port I/O Expander
Figure 1. MAX7300 Functional Diagram
MAX7300 is the recipient. When the MAX7300 is trans-
mitting to the master, the master generates the
acknowledge bit since the master is the recipient.
The MAX7300 has a 7-bit-long slave address (Figure 6).
The eighth bit following the 7-bit slave address is the
R/ W bit. It is low for a write command and high for a
read command.
The first 3 bits (MSBs) of the MAX7300 slave address
are always 100. Slave address bits A3, A2, A1, and A0
are selected by the address inputs, AD1 and AD0.
These two input pins can be connected to GND, V+,
SDA, or SCL. The MAX7300 has 16 possible slave
8
_______________________________________________________________________________________
P4 TO P31
AD0
AD1
SDA
SCL
D0
7-BIT DEVICE ADDRESS
GPIO DATA
MATCHER
SLAVE ADDRESS BYTE
ADDRESS
D1
8
7
GPIO
7
D2
Slave Address
CONFIGURATION
D3
DATA BYTE
R/W
R/W
8
D4
D5
D6
TO/FROM DATA REGISTERS
D7
DATA BYTE
addresses (Table 3), and therefore a maximum of 16
MAX7300 devices can share the same interface.
A write to the MAX7300 comprises the transmission of
the MAX7300’s slave address with the R/ W bit set to
zero, followed by at least 1 byte of information. The first
byte of information is the command byte. The com-
mand byte determines which register of the MAX7300
is to be written by the next byte, if received. If a STOP
condition is detected after the command byte is
received, then the MAX7300 takes no further action
(Figure 7) beyond storing the command byte.
PORT CHANGE
DETECTOR
D8
D9
D10
COMMAND BYTE
D11
Message Format for Writing
REGISTER DECODE
D12
COMMAND
DATA
COMMAND BYTE
PORT REGISTERS
8
MASK REGISTER
CONFIGURATION
TO COMMAND REGISTERS
D13
8
REGISTERS
CE
D14
R/W
D15
the MAX7300