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Roger 2016-12-19 02:49:18 -05:00
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Zelda-Microcode.md

@ -22,7 +22,6 @@ These are all the mails that the game sends to the DSP upon initialization:
Note that this command is available only in DMA version.
#### Command 0x1 (AKA DsetupTable)
```
@ -38,7 +37,6 @@ Note that this command is available only in DMA version.
These are all the mails that the game continuously sends to the DSP.
#### Command 0x2 (AKA DsyncFrame)
```
@ -52,7 +50,6 @@ These are all the mails that the game continuously sends to the DSP.
The Legend of Zelda: Wind Waker keeps sending these forever, alternating between three different sets of buffers.
### Synchronization Mails
```
@ -74,7 +71,6 @@ The Legend of Zelda: Wind Waker keeps sending these forever, alternating between
`CDD10003`
Sent by the CPU after DsyncFrame command has completed (and sent 0xDCD10005 to the CPU).
### Notes
The first command sent is 0xE. In the real Zelda ucode, this command is dummy. In the ucode used by SMG, it isn't the case.
@ -93,7 +89,6 @@ The number can probably vary from 0 to 15, though here it's only varying from 0
When receiving these mails, the ucode seems to store some values from the first mail into memory. These values are used only by command 0x2 (SyncFrame).
The purpose of that whole system is probably to keep mixing synchronous with the game's main loop.
## How the Zelda ucode interprets mails
The mails are interpreted by the exception 7 handler.
@ -102,7 +97,6 @@ This means that exception 7 is probably triggered when a new mail was received (
The first mail received determines how the following ones will be interpreted:
`0xXXXXGGGG`
### If G is zero
The whole mail is likely zero. The following mail will be formatted as follows:
@ -162,7 +156,6 @@ where:
- J is the address of the AFC coefficient table (64 bytes). You probably don't need it if you don't use AFC sounds.
- K is the address of 4 small parameter blocks. Their purpose isn't known yet. They seem to be intended for stuff like reverb.
### Playing sound
The DsyncFrame command is responsible for mixing, so if you want to hear any sound, you need to send DsyncFrame commands regularly:
@ -213,7 +206,6 @@ where G is the task to execute, as follows:
- 2: Do something and halt
- 3: Do nothing
This thing seems to be meant for debugging...
We recommend that you set G to 3 if you want to continue using the uCode.
You can set G to 0, 1 or 2 if you want to debug. Note that G=1 requires that you send 10 other mails. We don't know yet what they are.
@ -221,7 +213,6 @@ You can set G to 0, 1 or 2 if you want to debug. Note that G=1 requires that you
Phew. Now that your DsyncFrame successfully completed, you have to send another one, and another one...
## The parameter blocks
Like the well-known AX ucode, the Zelda ucode uses one parameter block (PB) per voice. (The number of voices is set by DsetupTable command).
@ -308,7 +299,6 @@ List of available sound formats:
- 0x0020: Raw PCM16 from RAM (not resampled)
- 0x0021: Raw PCM16 from RAM
## Unknown Registers?
The Zelda ucode accesses a memory region at 0xFF8X. At glance you may think it's accessing unknown DSP registers, but this is not the case.