XC886/888CLM
Memory Organization
User’s Manual
3-6
V1.3, 2010-02
Memory Organization, V 1.2
3.4
Memory Protection Strategy
The XC886/888 memory protection strategy includes:
•
Read-out protection: The user is able to protect the contents in the Flash (for Flash
devices) and ROM (for ROM devices) memory from being read.
– Flash protection is enabled by programming a valid password (8-bit non-zero
value) via BSL mode 6.
– ROM protection is fixed with the ROM mask and is always enabled.
•
Flash program and erase protection: This feature is available only for Flash devices.
3.4.1
Flash Memory Protection
As long as a valid password is available, all external access to the device, including the
Flash, will be blocked.
For additional security, the Flash hardware protection can be enabled to implement a
second layer of read-out protection, as well as to enable program and erase protection.
Flash hardware protection is available only for Flash devices and comes in two modes:
•
Mode 0: Only the P-Flash is protected; the D-Flash is unprotected.
•
Mode 1: Both the P-Flash and D-Flash are protected.
The selection of each protection mode and the restrictions imposed are summarized in
Table 3-1
Flash Protection Modes
Flash Protection Without hardware
protection
With hardware protection
Hardware
Protection Mode
-
0
1
Activation
Program a valid password via BSL mode 6
Selection
Bit 4 of password = 0 Bit 4 of password = 1
MSB of password = 0
Bit 4 of password = 1
MSB of password = 1
P-Flash
contents can be
read by
Read instructions in
any program memory
Read instructions in
the P-Flash
Read instructions in
the P-Flash or D-
Flash
External access
to P-Flash
Not possible
Not possible
Not possible
P-Flash program
and erase
Possible
Not possible
Not possible
*