Interprocessor (51-51d) protocol FAQ

The 51d program running on the 7312 and the Winbond '51 chip communicate over /dev/ttyS1 at 115200 bps.

Here is what we know so far about the communications protocol:

7312	8052	Possible Meaning
Initialization
0xf9		??
	0x53	??
0x10		??
	0x21	??
HU Query total disc
	0x21,0xdf	Query total disc
0xce		ACK
0x7D		Total Disks followstd>
	0xac	??
0x00		First byte
	0xbd	Continue
0x0f		Second Byte (total 15 disks)
	0xbd	Continue
0x74		End of Stream
	0xce	ACK
HU Query total tracks
	0x20,0x00,0x01,0xdf	Query total tracks in disc 1 (0x00, 0x01)
8052 Ping Request
	0x66, 0x9a	8052 PING
0xce		ACK
0x70		51d PONG
	0xce	ACK

• Heartbeat:

If the Winbond chip does not see a "heartbeat" signal every 10 seconds, it will kill power to the 7312 and reboot it. It's a two-part sequence:

7312 > 0x70
       0xAC   < 51
     > 0x90
       0xCE   < 51

Must repeat within 10 seconds, or the Winbond chip will output 0x66,0x9A 3 times and reboot.