09-03-2021, 05:50 PM
There are at least two versions of the PC85 menu system known as PC85 and PC85b.
PC85 has its menu code all contained within one ROM at the PAK 5 location.
PC85b however, has its menu code split across two ROMs to accommodate its expansion with the main menu at PAK 5 and the additional support at the PAK 10.
Interestingly, the PC85b also supports 16K PAK ROMs. This is accomplished by using the PAKPORT's D[2:0] select the desired PAK ROM /CS signal (as normal) and additionally D3 to select the upper or lower half (either %0000-%1FFFF or %2000-%3FFF).
For example: PAK 10 is actually the upper half of the 16K PAK 2 ROM.
The PC85 menu system relies upon non-standard and undocumented MWBASIC entry points to accomplish support of the MENU command syntax.
PC85 has its menu code all contained within one ROM at the PAK 5 location.
PC85b however, has its menu code split across two ROMs to accommodate its expansion with the main menu at PAK 5 and the additional support at the PAK 10.
Interestingly, the PC85b also supports 16K PAK ROMs. This is accomplished by using the PAKPORT's D[2:0] select the desired PAK ROM /CS signal (as normal) and additionally D3 to select the upper or lower half (either %0000-%1FFFF or %2000-%3FFF).
For example: PAK 10 is actually the upper half of the 16K PAK 2 ROM.
The PC85 menu system relies upon non-standard and undocumented MWBASIC entry points to accomplish support of the MENU command syntax.
