![](http://datasheet.mmic.net.cn/110000/MC3S12HZ256J3CAA_datasheet_3506324/MC3S12HZ256J3CAA_617.png)
Chapter 22 Module Mapping Control (MMCV4)
MC9S12HZ256 Data Sheet, Rev. 2.05
Freescale Semiconductor
617
In emulation modes, if the EMK bit in the MODE register (see MEBI block description chapter) is set, the
data and data direction registers for port K are removed from the on-chip memory map and become
external accesses.
22.4.2.2
Emulation Chip Select Signal
When the EMK bit in the MODE register (see MEBI block description chapter) is set, port K bit 7 is used
as an active-low emulation chip select signal, ECS. This signal is active when the system is in emulation
mode, the EMK bit is set and the FLASH or ROM space is being addressed subject to the conditions
EMK bit is clear, this pin is used for general purpose I/O.
22.4.2.3
External Chip Select Signal
When the EMK bit in the MODE register (see MEBI block description chapter) is set, port K bit 6 is used
as an active-low external chip select signal, XCS. This signal is active only when the ECS signal described
above is not active and when the system is addressing the external address space. Accesses to
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.
22.4.3
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 congured at system integration through
the use of the paging conguration switches (pag_sw1:pag_sw0) at the core boundary. The options
for easy reference).
Based upon the system conguration, the program page window will consider its access to be either
Table 22-16. 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
11
0K byte
1M byte