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L210 registers always return 0x0 instead of the last value stored

Applies to: AHB L210 L2CC

Scenario

When I do a write/read test on the following L210 registers, they all return 0x0.

  L2CC_CACHE_SYNC (offset 0x730)
  L2CC_INV_PA (offset 0x770)
  L2CC_CLEAN_PA (offset 0x7B0)
  L2CC_CLEAN_INV_PA (offset 0x7F0)
  L2CC_CLEAN_INV_IW (offset 0x7F8)
  L2CC_DBG_OP (offset 0xF00)
  L2CC_CLEAN_IW (offset 0x7B8)

Please can you tell me why this is?

Answer

All the registers you mention are indicated in table 2-2 in the TRM as "Read As Zero" (RAZ). This is not just the reset value; it is the value that will be returned every time a read is performed. Therefore, this is the correct value that you should see.

The reason is that these particular registers are used to initiate an action, rather than to store a value. It therefore makes no sense to return the previously-written value.

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