mc68hc908ap8a Freescale Semiconductor, Inc, mc68hc908ap8a Datasheet - Page 42

• Manufacturer Part Number: mc68hc908ap8a
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Memory
Before processing an interrupt, the CPU uses five bytes of the stack to save the contents of the CPU
registers.
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.
2.5 FLASH Memory
This sub-section describes the operation of the embedded FLASH memory. This memory can be read,
programmed, and erased from a single external supply. The program and erase operations are enabled
through the use of an internal charge pump.
2.5.1 Functional Description
The FLASH memory consists of an array of 62,368 bytes for user memory plus a block of 48 bytes for
user interrupt vectors and one byte for the mask option register. An erased bit reads as logic 1 and a
programmed bit reads as a logic 0. The FLASH memory page size is defined as 512 bytes, and is the
minimum size that can be erased in a page erase operation. Program and erase operations are facilitated
through control bits in FLASH control register (FLCR). The address ranges for the FLASH memory are:
Programming tools are available from Freescale. Contact your local Freescale representative for more
information.
1. No security feature is absolutely secure. However, Freescale’s strategy is to make reading or copying the FLASH difficult for
unauthorized users.
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$0860–$FBFF; user memory, 62,368 bytes
$FFD0–$FFFF; user interrupt vectors, 48 bytes
$FFCF; mask option register
Be careful when using nested subroutines. The CPU may overwrite data in
the RAM during a subroutine or during the interrupt stacking operation.
MC68HC908AP64A
MC68HC908AP32A
MC68HC908AP16A
MC68HC908AP8A
A security feature prevents viewing of the FLASH contents.
Device
For M6805 compatibility, the H register is not stacked.
MC68HC908AP A-Family Data Sheet, Rev. 3
FLASH Memory Size
NOTE
NOTE
(Bytes)
NOTE
62,368
32,768
16,384
8,192
Memory Address Range
$0860–$FBFF
$0860–$885F
$0860–$485F
$0860–$285F
(1)
Freescale Semiconductor