mc9s12xd256 Freescale Semiconductor, Inc, mc9s12xd256 Datasheet - Page 638

• Manufacturer Part Number: mc9s12xd256
• Description: Hcs12x Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Chapter 17 Memory Mapping Control (S12XMMCV2)
17.4.2.4
17.4.2.4.1
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
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
XGATE RAM size (XGRAMSIZE) could be lower or equal than the MCU RAM size (RAMSIZE).
The local address of the XGATE FLASH access is translated to the global address as defined by
Table
638
1
2
3
Internal Resource
XGRAMSIZE is the hexadecimal value of XGATE RAM SIZE in bytes.
FLASHSIZE is the hexadecimal value of FLASH SIZE in bytes.
$F800 is the hexadecimal value of the 64 Kilobytes minus 2 Kilobytes (Registers).
1-22.
The MCU FLASHSIZE is 64 Kbytes ($10000) and MCU RAMSIZE is 32 Kbytes ($8000).
The XGATE RAMSIZE is 16 Kbytes ($4000).
The space occupied by the XGATE RAM in the global address space will be:
XGATE accesses to local address range $0800–$BFFF will result in accesses to the following
FLASH block in the global address space:
Registers
FLASH
RAM
XGATE Memory Map Scheme
Bottom address: ($10_0000 minus $4000) = $0F_C000
Top address: $0F_FFFF
Bottom address: ($80_0000 minus $01_0000 plus $800) = $7F_0800
Top address: ($7F_0800 plus ($F800 minus $4000 minus $1)) = $7F_BFFF
Expansion of the XGATE Local Address Map
Table
1-22).
$10_0000 minus XGRAMSIZE
Table 17-21. XGATE Implemented Memory Space
FLASHSIZE plus $800
Bottom Address
$80_0000 minus
$00_0000
MC9S12XDP512 Data Sheet, Rev. 2.17
Example 17-3.
2
1
minus XGRAMSIZE minus $1
Bottom address plus $F800
Table
Top Address
1-22).
$0F_FFFF
$00_07FF
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