SPRUIU1C July 2020 – February 2024 DRA821U , DRA821U-Q1
There is a 30-bit free-running timer inside of the gasket. There is also a 2-bit eon bit. Whenever the timer is equal to or greater than the programmed timeout value (Timeout Value Register (Base Address + 0x14)), the timer is reset to 0 and the eon increments (when 3, the eon will roll-over to 0).
When a command is presented (the creq is asserted on the destination side) the command is given an eon value of the current eon minus 1 (for example, if the eon is currently 0, then the transaction is assigned an eon of 3). Thus each command has a minimum of 2 and a maximum of 3 eons before it times out. If the command is not accepted (cready does not assert) by the time the eon rolls around to the command eon, this is considered a Command Timeout. In this case:
Each transaction, once issued (cready is asserted), is assigned the current eon minus 1 (for example, if the eon is currently 0, then the transaction is assigned an eon of 3). Thus each transaction has a timeout of a minimum of 2 eons and a maximum of 3 (see Note below). If all of the responses for the transaction have not returned by the eon is equal to the transaction eon, this is considered a Transaction Timeout. In this case:
The timer only increments when the gasket is enabled.