S912XHZ512F1VAG Datasheet, PDF (878/978 Pages) Freescale Semiconductor, Inc – Covers MC9S12XHZ384, MC9S12XHZ256

Chapter 25 Memory Mapping Control (S12XMMCV3)
25.4.2.4 XGATE Memory Map Scheme
25.4.2.4.1 Expansion of the XGATE Local Address Map
The XGATE 64 Kbyte memory space allows access to internal resources only (Registers, RAM, and
FLASH). The 2 Kilobyte register address range is the same register address range as for the CPU and the
BDM module (see Table 25-22).
XGATE can access the FLASH in single chip modes, even when the MCU is secured. In expanded modes,
XGATE can not access the FLASH when MCU is secured.
The local address of the XGATE RAM access is translated to the global RAM address range. The XGATE
shares the RAM resource with the CPU and the BDM module (see Table 25-22).
XGATE RAM size (XGRAMSIZE) may be lower or equal to the MCU RAM size (RAMSIZE).
The local address of the XGATE FLASH access is translated to the global address as defined by
Table 25-22.
Table 25-22. XGATE Implemented Memory Space
Internal Resource
$Address
XGATE RAM
XGRAM_LOW = 0x0F_0000 plus (0x1_0000 minus XGRAMSIZE)¹
XGATE FLASH
XGFLASH_HIGH = 0x78_0000 plus (0xFFFF minus XGRAMSIZE)
1 _{XGRAMSIZE is the hexadecimal value of XGATE RAM SIZE in bytes.}
Example 25-3. is a general example of the XGATE memory map implementation.
Example 25-3.
The MCU FLASHSIZE is 64 Kbytes (0x10000) and MCU RAMSIZE is 32 Kbytes (0x8000).
The XGATE RAMSIZE is 16 Kbytes (0x4000).
The space occupied by the XGATE RAM in the global address space will be:
Bottom address: (0x10_0000 minus 0x4000) = 0x0F_C000
Top address: 0x0F_FFFF
XGATE accesses to local address range 0x0800–0xBFFF will result in accesses to the following
FLASH block in the global address space:
Bottom address: 0x78_0800
Top address: (0x78_FFFF minus 0x4000) = 0x78_BFFF
MC9S12XHZ512 Data Sheet, Rev. 1.06
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Freescale Semiconductor