Freescale Semiconductor, Inc.
GENERAL RELEASE SPECIFICATION
2.1
2.2
2.3
ROM
The user ROM consists of 48 bytes of page zero ROM from $0020 to $004F, 4096
bytes of ROM from $0100 to $10FF, and 16 bytes of user vectors from $1FF0 to
$1FFF. The self-check ROM and vectors are located from $1F00 to $1FEF.
ROM Security Feature
A security feature has been incorporated into the MC68HC05P4A to help prevent
external reading of code in the ROM. Placing unique customer code at ROM
locations $0028-$002F aids in keeping customer developed software proprietary.
RAM
The user RAM consists of 176 bytes of a shared stack area. The stack begins at
address $00FF. The stack pointer can access 64 bytes of RAM in the range
$00FF to $00C0.
NOTE
Using the stack area for data storage or temporary work locations
requires care to prevent it from being overwritten due to stacking
from an interrupt or subroutine call.
Rev. 2.0
2-3
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