SPRUI30H November 2015 – May 2024 DRA745 , DRA746 , DRA750 , DRA756
Some applications may require atomic reads of the 64 bits of a chained counter pair. An SCTM instance can be configured at synthesis time to provide an atomic read capability for one or more 64-bit counter pairs. When this capability is present, the designated counter pair provides atomic access when the correct read sequence is performed.
So when a chained counter has atomic read capability, an atomic counter value can be obtained by first reading the high-order counter followed by the low-order counter. Always observe this ordering, to prevent reading stale counter values from the low-order counter.
The shadow feature for chained counters is active only when the low-order counter is chained to a high-order counter. When functioning independently, the shadow feature is deactivated and a read of the counter always returns the current value.
To prevent sync errors introduced by the debugger, only application accesses activate the shadow feature. Debug qualified accesses always return the current value of the low-order counter, regardless of configuration.