TCA7408 Datasheet, PDF (7/25 Pages) Texas Instruments – Low-Voltage 8-Bit I2C and SMBus I/O Expander with Interrupt Output, RESET, I/ODirection Registers, and Programmable Pull-up/Pull-down

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REGISTER MAP
TCA7408
SCPS235 – NOVEMBER 2011
CONTROL REGISTER BITS
COMMAND
B7
B6
B5
B4
B3
B2
B1
B0 ^{BYTE (HEX)}
REGISTER
PROTOCOL
AI
0
0
0
0
0
0
1
01h
Device ID and Control Read (B7-B1) Write (B0)
AI
0
0
0
0
0
1
1
03h
I/O Direction
Read/write byte
AI
0
0
0
0
1
0
1
05h
Output State
Read/write byte
AI
0
0
0
0
1
1
1
07h
Output High-Impedance
Read/write byte
AI
0
0
0
1
0
0
1
09h
Input Default State
Read/write byte
AI
0
0
0
1
0
1
1
0Bh
Pull-up/down Enable
Read/write byte
AI
0
0
0
1
1
0
1
0Dh
Pull-up/down Select
Read/write byte
AI
0
0
0
1
1
1
1
0Fh
Input Status
Read byte
AI
0
0
1
0
0
0
1
11h
Interrupt Mask
Read/write byte
AI
0
0
1
0
0
1
1
13h
Interrupt Status
Read byte
POWER-UP
DEFAULT
0100 0010
0000 0000
0000 0000
1111 1111
0000 0000
1111 1111
0000 0000
xxxx xxxx
0000 0000
0000 0000
REGISTER DESCRIPTIONS
Register 01h – Device ID and Control
The Device ID and Control register contains the manufacturer ID and firmware revision. The Control register
indicates whether the device has been reset and the default values have been set.
• The Reset Interrupt is set B1=1 when the device is either reset by the RESET pin, a power on reset, or
software reset.
• Reset Interrupt is then cleared after being read by the master.
• Writing to B7–B1 has no effect on these bits in the register.
• A software reset is issued when the master writes B0=1.
• When reading from B0, the value read will always be 0.
BIT
DESCRIPTION
DEFAULT
B7
B6
B5
Manufacturer ID
0
1
0
B4
B3
B2
Firmware Revision
0
0
0
B1
Reset Interrupt
1
B0
Software Reset
0
Register 03h – I/O Direction
The I/O Direction Register configures the direction of the I/O pins.
• If a bit in this register is set to 0, the corresponding port pin is enabled as an input
• If a bit in this register is set to 1, the corresponding port pin is enabled as an output.
• When the port is set as an output the input buffers are disabled such that the bus can float.
BIT
DESCRIPTION
DEFAULT
B7
GPIO7
0
B6
GPIO6
0
B5
GPIO5
0
B4
GPIO4
0
B3
GPIO3
0
B2
GPIO2
0
B1
GPIO1
0
B0
GPIO0
0
Register 05h – Output Port Register
The Output Port Register sets the outgoing logic levels of the pins defined as outputs.
• When Bx is set to 0, GPIOx = L
• When Bx is set to 1, GPIOx = H
• Bit values in this register have no effect on pins defined as inputs
• Reads from this register reflect the value that is in the flip-flop controlling the output selection, not the actual
pin value.
BIT
DESCRIPTION
DEFAULT
B7
GPIO7
0
B6
GPIO6
0
B5
GPIO5
0
B4
GPIO4
0
B3
GPIO3
0
B2
GPIO2
0
B1
GPIO1
0
B0
GPIO0
0
Copyright © 2011, Texas Instruments Incorporated
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