MC908KX2MDWE Datasheet, PDF (31/210 Pages) Freescale Semiconductor, Inc – High-performance M68HC08 architecture, Fully upward-compatible object code with M6805, M146805, and M68HC05 Families

Random-Access Memory (RAM)
2.4 Random-Access Memory (RAM)
Addresses $0040–$00FF are RAM locations. The location of the stack RAM is programmable. The 16-bit
stack pointer allows the stack to be anywhere in the 64-Kbyte memory space.
NOTE
For correct operation, the stack pointer must point only to RAM locations.
Before processing an interrupt, the CPU uses five bytes of the stack to save the contents of the CPU
registers.
NOTE
For M6805, M146805 and M68HC05compatibility, the H register is not
stacked.
During a subroutine call, the CPU uses two bytes of the stack to store the return address. The stack
pointer decrements during pushes and increments during pulls.
NOTE
Be careful when using nested subroutines. The CPU could overwrite data
in the RAM during a subroutine or during the interrupt stacking operation.
2.5 FLASH Memory (FLASH)
The FLASH memory is an array of 7,680 bytes with an additional 36 bytes of user vectors and one byte
used for block protection.
NOTE
An erased bit reads as 1 and a programmed bit reads as 0.
The program and erase operations are facilitated through control bits in the FLASH control register
(FLCR). See 2.6 FLASH Control Register.
The FLASH is organized internally as an 8192-word by 8-bit complementary metal-oxide semiconductor
(CMOS) page erase, byte (8-bit) program embedded FLASH memory. Each page consists of 64 bytes.
The page erase operation erases all words within a page. A page is composed of two adjacent rows.
A security feature prevents viewing of the FLASH contents.⁽¹⁾
2.6 FLASH Control Register
The FLASH control register (FLCR) controls FLASH program and erase operations.
Address:
Read:
Write:
Reset:
$FE08
Bit 7
0
0
6
5
0
0
0
0
= Unimplemented
4
3
2
1
Bit 0
0
HVEN MASS ERASE PGM
0
0
0
0
0
Figure 2-3. FLASH Control Register (FLCR)
1. No security feature is absolutely secure. However, Freescale’s strategy is to make reading or copying the FLASH difficult for
unauthorized users.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
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