Datasheet

Chapter 3 Memory Mapping Control (S12XMMCV4)
MC9S12XE-Family Reference Manual Rev. 1.25
202 Freescale Semiconductor
The fixed 16K page from 0x4000–0x7FFF (when ROMHM = 0) is the page number 0xFD.
The reset value of 0xFE ensures that there is linear Flash space available between addresses 0x4000 and
0xFFFF out of reset.
The fixed 16K page from 0xC000-0xFFFF is the page number 0xFF.
3.3.2.7 RAM Page Index Register (RPAGE)
Read: Anytime
Write: Anytime
These eight index bits are used to page 4 KByte blocks into the RAM page window located in the local
(CPU or BDM) memory map from address 0x1000 to address 0x1FFF (see Figure 3-14). This supports
accessing up to 1022 KByte of RAM (in the Global map) within the 64 KByte Local map. The RAM page
index register is effectively used to construct paged RAM addresses in the Local map format.
CAUTION
XGATE write access to this register during an CPU access which makes use
of this register could lead to unexpected results.
Figure 3-14. RPAGE Address Mapping
NOTE
Because RAM page 0 has the same global address as the register space, it is
possible to write to registers through the RAM space when RPAGE = 0x00.
Address: 0x0016
76543210
R
RP7 RP6 RP5 RP4 RP3 RP2 RP1 RP0
W
Reset 11111101
Figure 3-13. RAM Page Index Register (RPAGE)
Bit18
Bit0
Bit11
0
Address [11:0]
RPAGE Register [7:0]
Global Address [22:0]
Bit12
Bit19
0
Address: CPU Local Address
or BDM Local Address
0