Keypad

Control

Control

Registers

and FIFO

Oscillator

(32 kHz)

Power-On

Reset

SDA

SCL

I C Bus

Control

2

RESET

INT

Interrupt

Control

VCC

ROW0 COL9

–

TCA6418E

www.ti.com

SCPS243 – SEPTEMBER 2012

SWITCHING CHARACTERISTICS

STANDARD MODE,

FAST MODE, FAST

MODE PLUS (FM+)

PARAMETER

FROM

TO

UNIT

I2C BUS

MIN

MAX

GPI_INT with

40

120

Debounce Enabled

tIV

Interrupt valid time

GPIO0-17

INT

μs

GPI_INT with

0

1

Debounce Disabled

tIR

Interrupt reset delay time

SCL

INT

1

μs

tPV

Output data valid

SCL

GPIO0-17

400

ns

tPS

Input data setup time

GPIO

SCL

0

ns

Debounce Disabled

tPH

Input data hold time

GPIO

SCL

300

ns

LOGIC DIAGRAM (POSITIVE LOGIC)

At power on, the GPIOs are configured as inputs with internal 50-k

Ω pulldown resistors enabled; however, the

system master can enable the GPIOs to function as inputs or outputs.

The system master can reset the TCA6418E in the event of a timeout or other improper operation by asserting a

low in the RESET input, while keeping the VCC at its operating level.

A reset can be accomplished by holding the RESET pin low for a minimum of tW. The TCA6418E registers and

I2C/SMBus state machine are changed to their default state once RESET is low (0). When RESET is high (1),

the I/O levels at the P port can be changed externally or through the master. This input requires a pullup resistor

to VCC, if no active connection is used.

The power-on reset puts the registers in their default state and initializes the I2C/SMBus state machine. The

RESET pin causes the same reset/initialization to occur without de-powering the part.

The open-drain interrupt (INT) output is used to indicate to the system master that an input state has changed.

INT can be connected to the interrupt input of a microcontroller. By sending an interrupt signal on this line, the

remote input can inform the microcontroller if there is incoming data on its ports without having to communicate

via the I2C bus. Thus, the TCA6418E can remain a simple slave device.

Copyright © 2012, Texas Instruments Incorporated

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