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Functional Description
MVME2500 Installation and Use (6806800L01H)
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The MVME2500 FPGA controls the chip select to SPI devices A and B. The FPGA chip select
control is based on the Switch Bank (S2-2).
At power-up, the selection of the SPI boot device is strictly based upon the Switch Bank (S2-2)
setting. Depending on the S2-2 setting, SPI_SEL0 is routed to one of two SPI devices. The
selected SPI device must contain a boot image. Once the boot image is copied into memory
and executed, the FPGA will wait and once the P20x0 will write on one bit of the FPGA
watchdog register, the FPGA will then pass through the SPI chip select from the P20x0 to SPI
device chip selects. The software can now perform read/write processes on any SPI device,
including copying from one SPI device to another.
With this flexible approach to firmware redundancy, one should always be able to recover from
a corrupt active firmware image, as long as a healthy firmware image is maintained in single
bootable SPI Device.
Figure 4-2 SPI Device Multiplexing Logic