PC912XDP512F0MPVR datasheet(633/1348 Pages) FREESCALE

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Chapter 17 Memory Mapping Control (S12XMMCV2)

MC9S12XDP512 Data Sheet, Rev. 2.21

Freescale Semiconductor

633

17.4.2.1.1

Expansion of the Local Address Map

Expansion of the CPU Local Address Map

The program page index register in MMC allows accessing up to 4 Mbyte of FLASH or ROM in the global

memory map by using the eight page index bits to page 256 16 Kbyte blocks into the program page

window located from address $8000 to address $BFFF in the local CPU memory map.

The page value for the program page window is stored in the PPAGE register. The value of the PPAGE

(see Section 1.5.1, “CALL and RTC Instructions”).

Control registers, vector space and parts of the on-chip memories are located in unpaged portions of the

64-kilobyte local CPU address space.

The starting address of an interrupt service routine must be located in unpaged memory unless the user is

certain that the PPAGE register will be set to the appropriate value when the service routine is called.

However an interrupt service routine can call other routines that are in paged memory. The upper

16-kilobyte block of the local CPU memory space ($C000–$FFFF) is unpaged. It is recommended that all

reset and interrupt vectors point to locations in this area or to the other upages sections of the local CPU

memory map.

Table 1-19 summarizes mapping of the address bus in Flash/External space based on the address, the

PPAGE register value and value of the ROMHM bit in the MMCCTL1 register.

The RAM page index register allows accessing up to 1 Mbyte –2 Kbytes of RAM in the global memory

map by using the eight RPAGE index bits to page 4 Kbyte blocks into the RAM page window located in

the local CPU memory space from address $1000 to address $1FFF. The EEPROM page index register

EPAGE allows accessing up to 256 Kbytes of EEPROM in the system by using the eight EPAGE index

bits to page 1 Kbyte blocks into the EEPROM page window located in the local CPU memory space from

address $0800 to address $0BFF.

Table 17-18. Global FLASH/ROM Allocated

Local

CPU Address

ROMHM

External

Access

Global Address

$4000–$7FFF

$7F_4000 –$7F_7FFF

Yes

$14_4000–$14_7FFF

$8000–$BFFF

N/A

No1

1 The internal or the external bus is accessed based on the size of the memory resources

implemented on-chip. Please refer to Figure 1-23 for further details.

$40_0000–$7F_FFFF

N/A

Yes1

$C000–$FFFF

N/A

$7F_C000–$7F_FFFF

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