AN 494: GPIO Pin Expansion Using I2C Bus Interface in Altera MAX Series

ID 683261
Date 9/22/2014
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1.2.2. GPIO Interface

Whenever the master issues a write condition (R/W=0), the data received on the I2C bus is used to update the general purpose output pins until a stop or a repeat start condition is encountered. Similarly, when the I2C master issues a read condition (R/W = 1), the values at the general purpose input pins are sampled at the ACK bit and transmitted serially over the I2C bus. This process continues until the master issues a stop or repeat start.

Table 2.  GPIO Pin Description
Signal Purpose Direction
8-bit Input General In
8-bit Output General Out