Model: World Championship Rally
Symptom: Stuck at Coprocessor Not Ready
Gaelco gave away the code to fix this game, but it requires a new battery to be installed and the code to be loaded.
Remove the cover from the center of the board. There's a set of 5 machine pin sockets with an O silkscreened next to them. The pinout starts from that O and is: 1) Vcc (don't use), 2) TXD, 3) RXD, 4) /PROG, 5) Ground
Connect a USB to TTL serial adapter to the header. These are easy to find and are used to program Arduino boards. The settings are 2400 Baud, 8 Bits, 1 Stop Bit, 0 Parity, and Xon/Xoff protocol.
If using RealTerm, set Hardware Flow Control to None and turn on both the Send and Receive Software Flow Control. Also set under the Send tab Delays: 2, 0 when sending the file.
Download this file:
http://foulweb.free.fr/divers/prog/WRDALLAS.HEXConnect to the game - you will need to power up the board. Press Enter and the game will display a banner. Send a U and the game will respond 'UNLOCKED', send an L then send the HEX file. When finished a > prompt will return. Send a Z and it will respond "LOCKED". If it fails, power cycle the board and start again. Slow down sending of the data if supported in your terminal software.
Reboot the game and the CoProcessor state should say OK and the game should boot.