When the Cortex-R5F processors are in the lock-step mode (This Figure), there should be code in the reset handler to ensure that the distributor within the GIC dispatches interrupts only to CPU0. During the lock-step operation, the TCMs that are associated with the redundant processor become available to the lock-step processor. The size of ATCM and BTCM become 128 KB each with BTCM supporting interleaved accesses from processor and AXI slave interface.
