Hi Russell,
very good example of code.
However assumption of port0 in 89c4051 is wrong.
it has ony port1 & port3.
Also your idea to store messages in ROM in Hex format is
not good. One can store messages in 'ASCII' format and then
dont have to convert same and waste time. In Metalink
assembler on has just to put 'TEXT' and it is done! Other
control characters including EOF = 03hex (I am not sure)can
be string terminator. These characters can be displayed with
4bit bus with 2 nibbles of 1character. One can assemble a nibble
in A and OR it with the 4bit of port (ANL p1,#0Fh clears the
bus pins and ORL p1,xxxx0000b send the data nibble.Then in
next you can setup E or other control pin.)
There is some important issue missing in this discussion:
There is 2wire LCD interface ckt on this or other site and
one need not use 6pins and Bit bang ! That is really very
cool thing with devices like 89cX051 where x=1,2,4.