12.3SSI PROGRAMMING

The SSI interface allows for a variety of software and hardware protocols.

νSignaling a read/write—In general, software uses the first write to the SSI to transmit an address or count to the peripheral. This value can include a read/write flag in the case where the device supports both reads and writes.

νUsing SSD1 as an address register—The SSD1 register can be an address register that holds the value of the last address accessed, and the SSD0 register can be the data transmit register. In this case, the current value in the SSD1 register can be used by software to generate the next address or to determine if the last transaction was a read or a write.

νUsing SSD1 and SSD0 as transmit registers for two peripheral devices—In some systems, it may clarify the code and aid in debugging to view the two data transmit registers as unique to different peripheral devices. This allows the last value transmitted to each device to be examined by debug code.

Synchronous Serial Interface

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AMD Am188TMER, Am186TMER user manual SSI Programming, Synchronous Serial Interface 12-7