How to Use SCM
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SPNU563A – March 2018
Copyright © 2018, Texas Instruments Incorporated
SCR Control Module (SCM)
3.3.3 How to Configure Timeout Check
The threshold compare block takes the real time counters (command request to command accepted and
command request to command response) from each IA of the interconnect hardware checker module and
compare against the corresponding threshold value in SCM every cycle. If any IA comparison fails, the
SCM module will update the corresponding status bit in SCMIAERR0STAT and SCMIAERR1STAT
registers. SCMIAERR0STAT logs the time out error for command request to command accepted.
SCMIAERR1STAT logs the time out error for command request to command response. Any status bit set
in these two status registers will trigger an error event to ESM (Error Signaling Module) and will not trigger
again until cleared by CPU.
You should configure the SCMTHRESHOLD control register to setup the command transaction request to
command transaction acceptance threshold as well as command transaction request to command
transaction response threshold. It is recommended that you use the default reset value of decimal 1024
(400h) for the SCMTHRESHOLD control registers. However, you can change this values depending on
application depending on the number of IA and TA required by the interconnect.
When threshold compare block triggers a time out error, the error will be sent to the ESM module resulting
in an interrupt exception to the CPU.
When interrupted, it is recommended that you read the SCMIAERR0STAT and SCMIAERR1STAT to find
out which master or slave having the time out issue and clear the real time counter inside interconnect.
Then, issue a retry on the transaction
1. If the retry is successful, you can resume operation.
2. If the retry fails because time out still occurs, you should trigger a self-test to check for any issue of
interconnect. If self-test fails or time out error still occurs after passing self-test, you should try to shut
down the system in a safe way. In the case that interconnect has issue and blocking access to Flash
or RAM, ESM pin action can not be reset thus external monitoring ASIC will be notified.
To clear real time counters inside SCR, you should switch to privilege mode and write Ah to the
SCMCNTRL[3:0] control register. The SCM module will reset the control key back to 5h once it triggers a
clear command to interconnect hardware checker. The interconnect hardware checker real time counter
needs to be reset to 0 in order to restart properly.