HCS08 datasheet(51/374 Pages) NXP

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Chapter 4 Memory

MC9S08JM60 Series Data Sheet, Rev. 5

Freescale Semiconductor

The RAM retains data when the MCU is in low-power wait, stop2, or stop3 mode. At power-on, the

contents of RAM are uninitialized. RAM data is unaffected by any reset provided that the supply voltage

does not drop below the minimum value for RAM retention.

For compatibility with older M68HC05 MCUs, the HCS08 resets the stack pointer to 0x00FF. In the

MC9S08JM60 series, it is usually best to re-initialize the stack pointer to the top of the RAM so the direct

page RAM can be used for frequently accessed RAM variables and bit-addressable program variables.

Include the following 2-instruction sequence in your reset initialization routine (where RamLast is equated

to the highest address of the RAM in the Freescale-provided equate file).

LDHX

#RamLast+1

;point one past RAM

TXS

;SP<-(H:X-1)

When security is enabled, the RAM is considered a secure memory resource and is not accessible through

BDM or through code executing from non-secure memory. See Section 4.6, “Security,” for a detailed

description of the security feature.

4.4

USB RAM

USB RAM is discussed in detail in Chapter 17, “Universal Serial Bus Device Controller (S08USBV1).”

4.5

Flash

The flash memory is used for program storage. In-circuit programming allows the operating program to

be loaded into the flash memory after final assembly of the application product. It is possible to program

the entire array through the single-wire background debug interface. Because no special voltages are

needed for flash erase and programming operations, in-application programming is also possible through

other software-controlled communication paths. For a more detailed discussion of in-circuit and

in-application programming, refer to the HCS08 Family Reference Manual, Volume I, Freescale

Semiconductor document order number HCS08RMv1.

4.5.1

Features

Features of the flash memory include:

•

Flash size

— MC9S08JM60 — 60,912 bytes (119 pages of 512 bytes each)

— MC9S08JM32 — 32,768 bytes (64 pages of 512 bytes each)

•

Single power supply program and erase

•

Command interface for fast program and erase operation

•

Up to 100,000 program/erase cycles at typical voltage and temperature

•

Flexible block protection

•

Security feature for flash and RAM

•

Auto power-down for low-frequency read accesses

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