Datasheet

Chapter 3 Module Mapping Control (MMCV4) Block Description
124 MC9S12C-Family / MC9S12GC-Family Freescale Semiconductor
Rev 01.24
unimplemented locations within the register space or to locations that are removed from the map (i.e., ports
A and B in expanded modes) will not cause this signal to become active. When the EMK bit is clear, this
pin is used for general purpose I/O.
3.4.3 Memory Expansion
The HCS12 core architecture limits the physical address space available to 64K bytes. The program page
index register allows for integrating up to 1M byte of FLASH or ROM into the system by using the six
page index bits to page 16K byte blocks into the program page window located from 0x8000 to 0xBFFF
in the physical memory space. The paged memory space can consist of solely on-chip memory or a
combination of on-chip and off-chip memory. This partitioning is configured at system integration through
the use of the paging configuration switches (pag_sw1:pag_sw0) at the core boundary. The options
available to the integrator are as given in Table 3-16 (this table matches Table 3-12 but is repeated here for
easy reference).
Based upon the system configuration, the program page window will consider its access to be either
internal or external as defined in Table 3-17.
NOTE
The partitioning as defined in Table 3-17 applies only to the allocated
memory space and the actual on-chip memory sizes implemented in the
system may differ. Please refer to the device overview chapter for actual
sizes.
Table 3-16. Allocated Off-Chip Memory Options
pag_sw1:pag_sw0 Off-Chip Space On-Chip Space
00 876K bytes 128K bytes
01 768K bytes 256K bytes
10 512K bytes 512K bytes
11 0K byte 1M byte
Table 3-17. External/Internal Page Window Access
pag_sw1:pag_sw0 Partitioning PIX5:0 Value
Page Window
Access
00 876K off-Chip,
128K on-Chip
0x0000–0x0037 External
0x0038–0x003F Internal
01 768K off-chip,
256K on-chip
0x0000–0x002F External
0x0030–0x003F Internal
10 512K off-chip,
512K on-chip
0x0000–0x001F External
0x0020–0x003F Internal
11 0K off-chip,
1M on-chip
N/A External
0x0000–0x003F Internal