MC9S08DZ96F2CLL datasheet(61/458 Pages) FREESCALE

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Chapter 4 Memory

MC9S08DZ128 Series Data Sheet, Rev. 1

Freescale Semiconductor

debug interface) and verifying that FLASH is blank. To avoid returning to secure mode after the next reset,

program the security bits (SEC) to the unsecured state (1:0).

4.4

Memory Management Unit

The memory management unit (MMU) allows the program and data space for the HCS08 Family of

Microcontrollers to be extended beyond the 64K CPU addressable memory map. The extended memory

when used for data can also be accessed linearly using a linear address pointer and data access registers.

4.4.1

Features

Key features of the MMU module are:

•

Memory Management Unit extends the HCS08 memory space

— up to 128K for program and data space

•

Extended program space using paging scheme

— PPAGE register used for page selection

— ﬁxed 16K byte memory window

— architecture supports eight 16K pages

•

Extended data space using linear address pointer

— 17-bit linear address pointer

— linear address pointer and data register provided in direct page allows access of complete

FLASH memory map using direct page instructions

— optional auto increment of pointer when data accessed

— supports a 2s complement addition/subtraction to address pointer without using any math

instructions or memory resources

— supports word accesses to any address speciﬁed by the linear address pointer when using

LDHX, STHX instructions

4.4.2

Memory Expansion

The HCS08 Core architecture limits the CPU addressable space available to 64K bytes. The Program Page

(PPAGE) allows for integrating up to 128K of FLASH into the system by selecting one of the 16K byte

blocks to be accessed through the Paging Window located at 0x8000-0xBFFF. The MMU module also

provides a linear address pointer that allows extension of data access up to 128K.

4.4.2.1

Program Space

The PPAGE register holds the page select value for the Paging Window. The value in PPAGE can be

manipulated by using normal read and write instructions as well as the CALL and RTC instructions. The

user should not change PPAGE directly when running from paged memory, only CALL and RTC should

be used.

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