TCA7408 Datasheet, PDF (11/25 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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TCA7408
SCPS235 – NOVEMBER 2011
Reads
The bus master first must send the TCA7408 address with the LSB set to a logic 0. The command byte is sent
after the address and determines which register is accessed.
After a restart, the device address is sent again but, this time, the LSB is set to a logic 1. Data from the register
defined by the command byte then is sent by the TCA7408.
Data is clocked into the register on the rising edge of the ACK clock pulse.
Figure 6. Read From Register
NOTE: ADDR = 0
Figure 7. Read From Input Status Register
Transfer of data can be stopped at any time by a Stop condition. When this occurs, data present at the latest
acknowledge phase is valid (output mode). It is assumed that the command byte previously has been set to 0Fh
(read Input Status Register). This figure eliminates the command byte transfer, a restart, and slave address call
between the initial slave address call and actual data transfer from GPIO.
Copyright © 2011, Texas Instruments Incorporated
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