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Question1: What is the default I/O drive strength of FX3/FX3S and how can it be configured?
Answer: As mentioned in section 10.4.4 of the FX3 TRM, the default I/O drive strength is Half Strength. The I/O Drive Strength Configuration Register, GCTL_DS, is configured with a default value of 2, which corresponds to Half Strength according to the following table from the FX3 TRM.
Table 1. Drive Strength Values
Three Quarter Strength
The drive strength for I/O pins is programmable even if the pin is configured for an alternate function. The I/O pin drive strength can be set to quarter strength, half strength, three-quarter strength, or full strength by configuring the appropriate bits in the GCTL_DS register. In the FX3 SDK, I/Os on the FX3 device are grouped into multiple interfaces (GPIF, I2C, I2S, SPI, UART) based on function. Refer to the FX3 API Guide of the FX3 SDK for details about APIs used for configuring the drive strength of these interfaces.
Note: FX3S’s S-port I/O drive strength is programmable similar to any other I/O pin as discussed in 4.1.2 I/O Drive Strength of the FX3 TRM.
Question2: What are the IOH and IOL values for different drive strengths?
Answer: IOH and IOL values for different strengths are mentioned in Table 9 of the FX3 datasheet.