MC68HC812A4 Datasheet, PDF (138/342 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
8.7.2 Chip-Select Control Register 1
Address: $003D
Bit 7
6
5
4
3
2
1
Bit 0
Read: 0
0
0
0
CSP1FL CSPA21 CSDHF CS3EP
Write:
Reset: 0
0
0
0
0
0
0
0
= Unimplemented
Figure 8-17. Chip-Select Control Register 1 (CSCTL1)
Read: Anytime
Write: Anytime
CSP1FL — Program Chip-Select 1 Covers Full Map
1 = If CSPA21 is cleared, chip-select program 1 covers the entire
memory map. If CSPA21 is set, this bit has no meaning or
effect.
0 = If CSPA21 is cleared, chip-select program 1 covers half the
map, $8000 to $FFFF. If CSPA21 is set, this bit has no
meaning or effect.
CSPA21 — Program Chip-Select Split Based on ADDR21
Setting this bit allows two 2-Mbyte memories to make up the 4-Mbyte
addressable program space. Since ADDR21 is always one in the
unpaged $C000 to $FFFF space, CSP0 is active in this space.
1 = Program chip-selects are both active (if enabled) for space
$8000 to $FFFF; CSP0 if ADDR21 is set and CSP1 if ADDR21
is cleared.
0 = CSP0 and CSP1 do not rely on ADDR21.
CSDHF — Data Chip-Select Covers Half the Map
1 = Data chip-select covers half the memory map ($0000 to $7FFF)
including the optional data page window ($7000 to $7FFF).
0 = Data chip-select covers only $7000 to $7FFF (the optional data
page window).
MC68HC812A4 — Rev. 3.0
138
Memory Expansion and Chip-Select
Advance Information
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