Changes

The processor exists in two versions: 7810 without internal ROM, and 7811 with 4K internal ROM. Normally, one would obviously use the ROM-less 7810 if one doesn't use the internal ROM - however. However, for some whatever reason, it seems to be quite common to use a 7811 with its internal ROM disabled.  The uPD781x datasheet doesn't contain useful info on how to do this, but the uPD78C1x (CMOS version) datasheet contains at least some fragments on how the MODE0 and MODE1 pins affect internal/external ROM mapping. Judging from that information, the following four combinations seem to be supported: