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Caution When a Pin is Assigned for SPI Slave in PSoC 4100S Plus - KBA230764

Caution When a Pin is Assigned for SPI Slave in PSoC 4100S Plus - KBA230764

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Translation - Japanese: PSoC 4100S PlusでピンがSPIスレーブに割り当てられている場合の注意 - KBA230764 - Community Translated (JA)


Why can I not choose SCB[3] for SPI Slave for PSoC® 4100S Plus 64-TQFP in PSoC Creator™?


SPI needs four pins for Master Out Slave In (MOSI), Master In Slave Out (MISO), Serial Clock (CLK), and Slave Select (SS), and these pins should be dedicated pins in the same serial communication block (SCB).

Also, SS for SPI Slave can be select0, even though SS for SPI Master select0, select1, and select2 can be chosen.

Availability of dedicated pins depend to be assigned depend on the package capacity. If all dedicated pins are not available for a certain package, you will not be permitted to use the corresponding block inside the device.

For example, in the PSoC 4100S Plus datasheet, “Alternate Pin Functions” states P6.0 (for MOSI), P6.1(for MISO), P6.2 (CLK), and P6.3 (SS) are dedicated pins for the SPI Slave instance of SCB[3] for PSoC 4100S Plus device, as shown Figure 1. P6[3] – P6[5], highlighted in blue, is for SS in SCB[3], but SS for SPI Slave can be just P6[3] because of select0.

Figure 1. Alternate Pin Function


According to the Pinout in the PSoC 4100S Plus datasheet , P6[3] is not available in 64-TQFP device. See Figure 2.

Figure 2. Pin List of Pinout


Check the pins in the pin list (Figure 2) carefully, because some pins are disabled depending on the package capacity. Therefore, it is recommended to use other SCB blocks for SCB SPI instead of SCB[3].

When a block is required to be used, check "Alternate Pin Function" in PSoC 4100S Plus datasheet to avoid choosing a block that is not available inside the device.

It is recommended to check Pinout when using other peripherals as well as SPI.

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