MC68HC05JJ6 Datasheet, PDF (37/216 Pages) Freescale Semiconductor, Inc – General Release Specification Microcontrollers

Memory
2.7 ROM
The ROM is located in three areas of the memory map:
• Addresses $0700–$1EF7 contain 6136 bytes of user ROM.
• Addresses $1EF8–$1EFF contain eight bytes for security code.
• Addresses $1FF0–1FFF contain 16 bytes of ROM reserved for
user vectors and COP register.
2.8 ROM Security
The MC68HC05JJ6/MC68HC05JP6 contains a ROM security feature¹
that requires that the proper data sequence be presented to port B
before the internal ROM contents can be read in any of the expanded
bus modes used for testing. The bytes to match are placed at ROM
locations $1EF8 through $1EFF as shown in Figure 2-6.
Address
$1EF8
$1EF9
$1EFA
$1EFB
$1EFC
$1EFD
$1EFE
$1EFF
Register Name
1st ROM Security Check Byte
2nd ROM Security Check Byte
3rd ROM Security Check Byte
4th ROM Security Check Byte
5th ROM Security Check Byte
6th ROM Security Check Byte
7th ROM Security Check Byte
8th ROM Security Check Byte
Figure 2-6. ROM Security Bytes
1. No security feature is absolutely secure. However, Freescale’s strategy is to make reading or
copying the ROM difficult for unauthorized users.
MC68HC05JJ6/MC68HC05JP6 — Rev. 3.2
Freescale Semiconductor
Memory
General Release Specification
37