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:

• 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.