Chapter 23 Memory Mapping Control (S12XMMCV2)
MC9S12XDP512 Data Sheet, Rev. 2.11
Freescale Semiconductor 909
The following conditions must be satisfied to ensure correct operation of the RAM protection mechanism: Value stored in RAMXGU must be lower than the value stored in RAMSHL. Value stored RAMSHL must be lower or equal than the value stored in RAMSHU.

Figure 23-25. RAM Write Protection Scheme

Table 23-22. RAM Write Protection Interrupt Vectors

Interrupt Source CCR Mask Local Enable
CPU access violation I Bit AVIE in RAMWPC
$0F_FFFF
$00_0000
Shared Region
XGATE RAM
Region
$0F_RAMSHU_FF
$0F_RAMSHL_00
$0F_RAMXGU_FF
Only XGATE is allowed to write
CPU and XGATE are allowed to write
Only CPU is allowed to write
Unimplemented
Only CPU is allowed to write
RAMSIZE
$00_0800
2K Registers