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[SC64][DOCS] Updated memory map documentation

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Mateusz Faderewski 2022-12-28 15:26:10 +01:00
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docs/memory_map.md
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@ -47,9 +47,13 @@ This mapping is used when accessing flashcart from N64 side.
## SC64 registers
SC64 contains small register region used for communication between N64 and controller code running on the μC.
Protocol is command based with support for up to 256 diferrent commands and two 32-bit argument/result values per operation.
Support for interrupts is provided but currently no command relies on it, 64DD IRQ is handled separately.
| name | address | size | access | usage |
| ------------------ | ------------- | ------- | ------ | -------------------------------- |
| **STATUS/COMMAND** | `0x1FFF_0000` | 4 bytes | RW | Command execute and status |
| **STATUS/COMMAND** | `0x1FFF_0000` | 4 bytes | RW | Command execution and status |
| **DATA0** | `0x1FFF_0004` | 4 bytes | RW | Command argument/result 0 |
| **DATA1** | `0x1FFF_0008` | 4 bytes | RW | Command argument/result 1 |
| **VERSION** | `0x1FFF_000C` | 4 bytes | RW | Hardware version and IRQ clear |
@ -104,3 +108,14 @@ Value `0x00000000` will reset sequencer state.
Two consequentive writes of values `0x5F554E4C` and `0x4F434B5F` will unlock all SC64 registers if flashcart is in lock state.
Value `0xFFFFFFFF` will lock all SC64 registers if flashcart is in unlock state.
---
### Command execution flow
1. Check if command is already executing by reading `CMD_BUSY` bit in **STATUS/COMMAND** register (optional).
2. Write command argument values to **DATA0** and **DATA1** registers, can be skipped if command doesn't require it.
3. Write command ID to **STATUS/COMMAND** register.
4. Wait for `CMD_BUSY` bit in **STATUS/COMMAND** register to go low.
5. Check if `CMD_ERROR` bit in **STATUS/COMMAND** is set:
- If error is set then read **DATA0** register containing error code.
- If error is not set then read **DATA0** and **DATA1** registers containing command result values, can be skipped if command doesn't return any values.