Agilex™ 7 Hard Processor System Technical Reference Manual

ID 683567
Date 8/13/2024
Public
Document Table of Contents

16.4.3.1. Command Path

The command path performs the following functions:
  • Load card command parameters
  • Send commands to card bus
  • Receive responses from card bus
  • Send responses to BIU
  • Load clock parameters
  • Drives the P‑bit on command pin

A new command is issued to the controller by writing to the BIU registers and setting the start_cmd bit in the cmd register. The command path loads the new command (command, command argument, timeout) and sends an acknowledgement to the BIU.

After the new command is loaded, the command path state machine sends a command to the card bus—including the internally generated seven‑term CRC (CRC‑7)—and receives a response, if any. The state machine then sends the received response and signals to the BIU that the command is done, and then waits for eight clock cycles before loading a new command. In CE‑ATA data payload transfer (RW_MULTIPLE_BLOCK) commands, if the card device interrupts are enabled (the nIEN bit is set to 0 in the ATA control register), the state machine performs the following actions after receiving the response:

  • Does not drive the P‑bit; it waits for CCS, decodes and goes back to idle state, and then drives the P‑bit.
  • If the host wants to send the CCSD command and if eight clock cycles are expired after the response, it sends the CCSD pattern on the command pin.