Command Controller

Zynq UltraScale+ Device Technical Reference Manual (UG1085)

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2.4 English

The SD command control generates the command sequence on the CMD line of the SD interface for every new command programmed by the software. The command control controller also implements the response reception and checking the validity of the response. It uses the response type field to determine the length of the response and the presence of the CRC7 field. The response is received on the receive clock, which is either the looped back clock or the tuned clock. After the response is received, the contents of the response (start bit, command index, CRC7, end bit) are verified and the response status is written to registers, setting various status bits. The controller also implements a timeout check on the response reception to make sure that the response is received within the defined time (5 or 64 clocks based on command type). The received response is stored into the appropriate bit position in the response register. The SD command controller generates controls to the SD transmit control and SD receive control based on the transfer direction. The SD command controller also generates an auto command (AutoCMD12 or AutoCMD23) when enabled.