J041 SCPUB
The memory map can be altered by three options:
Start End | ||||
0K | 0000 3FFF |
IC22 (16K) | STEbus | If on-board EPROM is
disabled, all accesses before 8000 are STEbus accesses. If EPROMs smaller than 16K are
used, |
16K | 4000 7FFF |
IC23 (16K) | ||
32K | 8000 BFFF |
STEbus | ||
48K | C000 DFFF |
IC20(8K) | If on-board RAM is
disabled, all accesses after 8000 are STEbus accesses. |
|
56K | E000 EFFF |
Unused | IC21(8K) | |
60K | F000 F7FF | IC20 (2K) | ||
62K | F800 FFFF | IC21 (2K) |
The address that is put on the bus during memory bus accesses is the same as the Z80 address: there is no translation. The Z80 address is 16 bits, however, and the STEbus address is 20 bits. The extra four bits come from the control latch, and these should be set to the correct value before the bus access is attempted.
Avoid switching memory from a program running in an area of memory that will be switched out, because the program will disappear as soon as the memory is switched!