TCA7408 Datasheet, PDF (8/25 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

TCA7408
SCPS235 – NOVEMBER 2011
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Register 07h – Output High-Impedance
The Output High-Impedance Register determines whether pins set as output are enabled or high-impedance
• When a bit in this register is set to 0, the corresponding GPIO-port output state follows register the output port
register (05h).
• When a bit in this register is set to 1, the corresponding GPIO-port output is set to high-impedance.
• Bit values in this register have no effect on pins defined as inputs. In turn, 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
1
B6
GPIO6
1
B5
GPIO5
1
B4
GPIO4
1
B3
GPIO3
1
B2
GPIO2
1
B1
GPIO1
1
B0
GPIO0
1
Register 09h – Input Default State
The Input Default State Register sets the default state of the GPIO-port input for generating interrupts.
• When a bit in this register is set to 0, the default for the corresponding input is set to LOW
• When a bit in this register is set to 1, the default for the corresponding input is set to HIGH
• Bit values in this register have no effect on pins defined as outputs. In turn, reads from this register reflect the
value that is in the flip-flop controlling the default state, not the actual pin value.
BIT
DESCRIPTION
DEFAULT
B7
GPIO7
1
B6
GPIO6
1
B5
GPIO5
1
B4
GPIO4
1
B3
GPIO3
1
B2
GPIO2
1
B1
GPIO1
1
B0
GPIO0
1
Register 0Bh – Pull-up/-down Enable
The Pull-up/-down Enable Register enables or disables the pull-up/down resistor on the GPIO-port as defined in
the Pull-up/down Select Register (0Dh).
• When a bit in this register is set to 0, the pull-up/down on the corresponding GPIO is disabled.
• When a bit in this register is set to 1, the pull-up/down on the corresponding GPIO is enabled.
BIT
DESCRIPTION
DEFAULT
B7
GPIO7
1
B6
GPIO6
1
B5
GPIO5
1
B4
GPIO4
1
B3
GPIO3
1
B2
GPIO2
1
B1
GPIO1
1
B0
GPIO0
1
Register 0Dh – Pull-up/-down Select
The Pull-up/down Select Register allows the user to select either a pull-up or pull-down on the GPIO-port. This
register only selects the pull-up/down resistor on the GPIO-port, while the enabling/disabling is controlled by the
Pull-up/down Enable Register (0Bh).
• When a bit in this register is set to 0, the pull-down on the corresponding GPIO is selected.
• When a bit in this register is set to 1, the pull-up on the corresponding GPIO is selected.
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
8
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