Module Operation
505
SPNU563A – March 2018
Copyright © 2018, Texas Instruments Incorporated
CPU Compare Module for Cortex-R5F (CCM-R5F)
13.2.3 Checker CPU Inactivity Monitor
Similar to the CPU / VIM Output Compare Diagnostic, the Checker CPU Inactivity Monitor can also run in
one of the following four operating modes:
1. Active compare
2. Self-test
3. Error forcing
4. Self-test error forcing
The operating mode can be selected by writing a dedicated key to the key register (MKEY3).
13.2.3.1 Active Compare Mode
This is the default mode on start-up. In this mode, several key bus signals such as the bus valid control
signals from the checker CPU that would have indicated a valid bus transaction onto the interconnect are
compared against their clamped safe values. While the two CPUs are in lockstep configuration, the
outputs of the checker CPU are supposed to clamp to the inactive state that is all zeros. A difference
between the checker CPU compare bus outputs and their respective inactive states is indicated by
signaling an error to the ESM which sets the error flag "CCM-R5F - CPU1 AXIM Bus Monitor Failure".
Table 13-5. Checker CPU Signals to Monitor
Signals
Remark
AWVALIDM
When asserted, indicates address and control are valid on the Checker CPU's AXI master port for
write transaction.
ARVALIDM
When asserted, indicates address and control are valid on the Checker CPU's AXI master port for
read transaction.
AWVALIDP
When asserted, indicates address and control are valid on the Checker CPU's AXI peripheral port
for write transaction.
ARVALIDP
When asserted, indicates address and control are valid on the Checker CPU's AXI peripheral port
for read transaction.
BVALIDS
When asserted, indicates that a valid write response is available on the Checker CPU's AXI slave
port for write transaction
RVALIDS
When asserted, indicates address and control are valid on the Checker CPU's AXI slave port for
read transaction
13.2.3.2 Self-Test Mode
Similar to the other self-test described for CPU / VIM Output Compare Diagnostic, the Checker CPU
Inactivity Monitor can be placed in self-test mode. In self-test mode, the CCM-R5F checks the Checker
CPU Inactivity Monitor itself for faults. During self-test, the compare error module output signal is
deactivated. Any fault detected inside the CCM-R5F will be flagged by ESM error “CCM-R5F - self-test”.
In self-test mode, the CCM-R5F automatically generates test patterns to look for any hardware faults. If a
fault is detected, then a self-test error flag is set, a self-test error signal is asserted and sent to the ESM,
and the self-test is terminated immediately. If no fault is found during self-test, the self-test complete flag is
set. In both cases, the CCM-R5F Checker CPU Inactivity Monitor Diagnostic remains in self-test mode
after the test has been terminated or completed, and the application needs to switch the CCM-R5F mode
by writing another key to the mode key register (MKEY3). During the self-test operation, the compare error
signal output to the ESM is inactive irrespective of the compare result.
There are also two types of patterns generated by CCM-R5F during self-test mode for Check CPU
Inactivity Monitor. The difference here is the number of test patterns applied during self-test.
i.
Compare Match Test
ii. Compare Mismatch Test
CCM-R5F first generates Compare Match Test patterns, followed by Compare Mismatch Test patterns.
