Replacing SPI SST25WF040 component on T4240QDS

[bryantheriault]

Folks, the documentation is unclear to me on the use of this device. Section 2.10 of the T4240QDS_RM_V9.1_130604.pdf states that this is a SPI EEPROM device and further states that "Other devices and chip selects can be evaluated by replacing the device and re-wiring the board". Looking up the data sheet for the component in question, this is labeled as a 1.8 V Serial Flash. What I don't know is: (1) is this chip needed for any boot processes or critical board operations by design, or is this a completely optional part which can be removed with no ill effects? (2) If I replace this part, must I replace it with a similar component, or can I place any SPI 1.8V compatible component in its place? (3) When the documentation refers to rewiring the board, does this mean simply desoldering the SST25WF040 and soldering a new pin-matched component in its place?

[alexander_yakov · Accepted solution]

1. The T4240 device support a big number of boot options, the device connected to SPI is definitely not the device absolytely required for proper board operation.

2. SPI controller is configurable, so the only mandatory requirement here is 1.8V power supply for SPI controller pins and, therefore, for SPI device connected.

3. I think this means not only replacing the SPI device, but also populating the resistor to another position to select another chip select line, see Figure 2-17 for non populated resistors.