durgadas311
Veteran Member
One of the reasons I suspected the ROM was faded or did not read correctly is that there is a non-sense instruction in the RST 7 code, at location 0043h. The instruction there is "move A to A", and looking at the surrounding code it is almost-certain that it should be "move A to B", as the code appears to be toggling bit 2 of the B register. It is also possible that this is a software bug that was just never found, if that code did not get used/tested.