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Or1ksim Memory Controller problems

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Information:
Type :: BUG
Status :: CLOSED
Assigned to :: Jeremy, Bennett

Description:

The Or1ksim memory controller has problems.

1. The startup code sets the BA_MASK register for 64MB memory blocks. This means that if a smaller block of memory has been declared in the configuration file, then accesses to higher addresses, but less than 64MB will be allowed, but with no memory allocated, cause a segfault (see verify_memoryarea in memory.c).

2. Enabling the memory controller causes memory at 0xf0000000 to be mirrored at 0x00000000. This means programs loaded in flash at 0xf0000000 work out of the box. However without the MC enabled this does not happen. The correct solution (in both cases) is to set the EPH bit in SR in the CPU configuration section. This needs more investigation, since I haven't seen what triggers this.

3. Disabling the memory controller causes problems with the standard library startup code, since it expects to configure a memory controller at 0x93000000. This will cause lots of memory access errors. The workaround is to declare a 128B memory block at address 0x93000000.

These problems need further investigation (and probably splitting into 3 bugs). Placed here for the record.

Jeremy

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