MC68HC812A4 Datasheet, PDF (134/342 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
PWEN — Program Window Enable Bit
1 = Enables paging of the program space
(16 Kbytes: $8000–$BFFF) via the PPAGE register
0 = Disables PPAGE
EWEN — Extra Window Enable Bit
1 = Enables paging of the extra space (1 Kbyte) via the EPAGE
register
0 = Disables EPAGE
8.5.9 Memory Expansion Assignment Register
Address: $0038
Bit 7
6
5
4
3
2
1
Bit 0
Read: 0
Write:
0
A21E A20E A19E A18E A17E A16E
Reset: 0
0
0
0
0
0
0
0
= Unimplemented
Figure 8-15. Memory Expansion Assignment Register (MXAR)
Read: Anytime
Write: Anytime
A21E, A20E, A19E, A18E, A17E, and A16E — Selects the memory
expansion pins ADDR21–ADDR16.
1 = Selects memory expansion for the associated bit function,
overrides DDRG
0 = Selects general-purpose I/O for the associated bit function
In single-chip modes these bits have no effect.
MC68HC812A4 — Rev. 3.0
134
Memory Expansion and Chip-Select
Advance Information
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