P912XDP512F0MFVR datasheet(638/1350 Pages) FREESCALE

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Chapter 17 Memory Mapping Control (S12XMMCV2)

MC9S12XDP512 Data Sheet, Rev. 2.17

638

Freescale Semiconductor

17.4.2.4

XGATE Memory Map Scheme

17.4.2.4.1

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 1-22).

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 1-22).

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 1-22.

Example 17-3.

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:

Bottom address: ($10_0000 minus $4000) = $0F_C000

Top address: $0F_FFFF

XGATE accesses to local address range $0800–$BFFF will result in accesses to the following

FLASH block in the global address space:

Bottom address: ($80_0000 minus $01_0000 plus $800) = $7F_0800

Top address: ($7F_0800 plus ($F800 minus $4000 minus $1)) = $7F_BFFF

Table 17-21. XGATE Implemented Memory Space

Internal Resource

Bottom Address

Top Address

Registers

$00_0000

$00_07FF

RAM

$10_0000 minus XGRAMSIZE1

1 XGRAMSIZE is the hexadecimal value of XGATE RAM SIZE in bytes.

$0F_FFFF

FLASH

$80_0000 minus

FLASHSIZE plus $8002

2 FLASHSIZE is the hexadecimal value of FLASH SIZE in bytes.

Bottom address plus $F800

minus XGRAMSIZE minus $13

3 $F800 is the hexadecimal value of the 64 Kilobytes minus 2 Kilobytes (Registers).

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