[Coco] 6309/6809 opcodes with mixed 8/16 bit registers

[Luis Antoniosi]

> as Halt and Catch Fire. It actually did not catch fire but the processor went into an address
> self test mode that had to be hard resetted to continue. There maybe other test mode
> opcodes that may or may not be there. Some may appear to do nothing but actually do

in theory a Core-Memory computer could literally catch fire if the
processor is halted reading the same address...

but this must be another urban legend...  :P