LS1012A - muxing SPI and GPIO

[luka_pirnat]

Hello,

we're designing a LS1012-based board and we'll be using SPI only to load FPGA configuration, therefore we only need SPI_CLK and SPI_MOSI signals. So, I'd like to know whether it's possible to use the remaining SPI signal pins as GPIOs (GPIO1_25, _26, _27, _28)? I found conflicting info on here (LS1043A, GPIO Query), so I'm not sure. I did check the PinMux tool and it seems it's possible.

Regards,
Luka

[alexander_yakov · Accepted solution]

Please refer to LS1012A Reference Manual, Table 4-10 "RCW Field descriptions".

You can see that SPI_MOSI, SPICS0_B, SPI_CLK are configured in group by one RCW field "SDHC2_BASE_BASE", whereas other pins SPI_MISO, SPICS2_B, SPI_CS1_B are configured by other field "SDHC2_BASE_DAT321". This mease your can configure only first three pins to SPI functions by SDHC2_BASE_BASE="11", leaving other three pins configured as GPIO1[26,27,28] by SDHC2_BASE_DAT321="00" and SDHC2_EXT_* = "0"

[luka_pirnat]

Yes, I actually checked the ref. manual, Table 3-6 (SDHC2_BASE signal configuration), but I suppose I misinterpreted it. However I do understand now: once I set RCW[SDHC2_BASE_BASE] to 0b11, I cannot use these three signals for anything else but SPI. Thanks!