MC68HC812A4 Datasheet, PDF (137/342 Pages) Motorola, Inc – 16-bit device composed of standard on-chip peripheral modules connected by an intermodule bus. Modules include

Memory Expansion and Chip-Select
Chip-Select Registers
CS3E — Chip-Select 3 Enable Bit
1 = Enables this chip-select which covers a 128-byte space
following the register space ($x280–$x2FF or $xA80–$xAFF)
Alternately, it can be active for accesses within the extra page
window.
0 = Disables this chip-select
CS2E — Chip-Select 2 Enable Bit
1 = Enables this chip-select which covers a 128-byte space
following the register space ($x380–$x3FF or $xB80–$xBFF)
0 = Disables this chip-select
CS1E — Chip-Select 1 Enable Bit
CS2 and CS3 have a higher precedence and can override CS1 for a
portion of this space.
1 = Enables this chip-select which covers a 256-byte space
following the register space ($x300–$x3FF or $xB00–$xBFF)
0 = Disables this chip-select
CS0E — Chip-Select 0 Enable Bit
CS1, CS2, and CS3 have higher precedence and can override CS0
for portions of this space.
1 = Enables this chip-select which covers a 512-byte space
following the register space ($x200–$x3FF or $xA00–$xBFF)
0 = Disables this chip-select
Advance Information
MOTOROLA
Memory Expansion and Chip-Select
MC68HC812A4 — Rev. 3.0
137