What's on that Access Port?

In my last post, I wrote about debugging the Nordic Semiconductor nRF54LM20 when a peripheral, specifically the Key Management Unit (KMU), writes directly to memory while the CPU is halted. Or I should really say that I wrote about debugging the application core (Cortex-M33), as the nRF54LM20 also has a RISC-V coprocessor (VPR) referred to as the Fast Lightweight Peripheral Processor (FLPR). Around the time that Nordic announced the VPR core, I wrote two posts; one about its architecture and the other about how communication works between it and an application core.