MC9S08SH8CTJ Datasheet, PDF (50/341 Pages) Freescale Semiconductor, Inc – MC9S08SH8 Datasheet

Chapter 4 Memory
4.4 RAM
The MC9S08SH8 includes static RAM. The locations in RAM below 0x0100 can be accessed using the
more efficient direct addressing mode, and any single bit in this area can be accessed with the bit
manipulation instructions (BCLR, BSET, BRCLR, and BRSET). Locating the most frequently accessed
program variables in this area of RAM is preferred.
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 (V_RAM).
For compatibility with M68HC05 MCUs, the HCS08 resets the stack pointer to 0x00FF. In the
MC9S08SH8, it is usually best to reinitialize 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 Semiconductor-provided equate file).
LDHX
TXS
#RamLast+1
;point one past RAM
;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.
4.5 FLASH
The FLASH memory is intended primarily 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/D.
MC9S08SH8 MCU Series Data Sheet, Rev. 3
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Freescale Semiconductor