MC68HC812A4 Datasheet, PDF (130/342 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
8.5 Memory Expansion Registers
This section describes the memory expansion registers.
8.5.1 Port F Data Register
Address: $0030
Bit 7
6
5
4
3
2
1
Bit 0
Read: 0
Write:
PF6
PF5
PF4
PF3
PF2
PF1
PF0
Reset: 0
0
0
0
0
0
0
0
= Unimplemented
Alternate pin function:
CSP1 CSP0 CSD
CS3
CS2
CS1
CS0
Figure 8-7. Port F Data Register (PORTF)
Read: Anytime
Write: Anytime
Seven port F pins are associated with chip-selects. Any pin not used as
a chip-select can be used as general-purpose I/O. All pins are pulled up
when inputs (if pullups are enabled). Enabling a chip-select overrides the
associated data direction bit and port data bit.
8.5.2 Port G Data Register
Address: $0031
Bit 7
6
5
4
3
2
1
Bit 0
Read: 0
Write:
0
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Reset: 0
0
0
0
0
0
0
0
= Unimplemented
Alternate pin function:
ADDR21 ADDR20 ADDR19 ADDR18 ADDR17 ADDR16
Figure 8-8. Port G Data Register (PORTG)
Read: Anytime
Write: Anytime
Six port G pins are associated with memory expansion. Any pin not used
for memory expansion can be used as general-purpose I/O. All pins are
pulled up when inputs (if pullups are enabled). Enabling a memory
expansion address with the memory expansion assignment register
overrides the associated data direction bit and port data bit.
MC68HC812A4 — Rev. 3.0
130
Memory Expansion and Chip-Select
Advance Information
MOTOROLA