SPRUJB6B November 2024 – May 2025 AM2612
The Command FIFO status transitions are depicted in Figure 7-118. Command transactions via AHB interface are decoded and sent to command FIFO in command and interrupt controller (CIC) block for MAU commands and sent to MCG for MCG commands. Depending on the depth of the command FIFO (set to 2), multiple MAU commands can be written to the FIFO till it is full. However, there is no FIFO to store MCG commands, so only one command can be written at a time which is stored in an internal register residing in MCG block. This should not lead to any performance impact as MCG commands typically take thousands of cycles to complete. The internal command FIFO is reset when an MCG/MAU panic/error is encountered as well as when pkeFlush bit (bit 20) in AHB register PKE_RESET_CTRL is written.
As depicted in Figure 7-118, FIFO can move to ERROR state from EMPTY state in these scenarios:
Writing two back to back MCG commands assuming the 1st command does not complete in 1 cycle.
Writing >3 MAU commands assuming FIFO is 2-deep and the 1st command written is popped by MAU core for execution.