XC858CA
Functional Description
3.2.1 Memory Protection Strategy
The XC858 memory protection strategy includes:
• Basic protection: The user is able to block any external access via the boot option to
any memory
• Read-out protection: The user is able to protect the contents in the Flash
• Flash program and erase protection
These protection strategies are enabled by programming a valid password (16-bit non-
one value) via Bootstrap Loader (BSL) mode 6.
3.2.1.1 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.
Table 3
Flash Protection Modes
Flash
Without hardware
Protection protection
With hardware protection
Hardware -
Protection
Mode
0
1
Activation Program a valid password via BSL mode 6
Selection
Bit 13 of password = 0 Bit 13 of password = 1 Bit 13 of password = 1
MSB of password = 0 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
Not possible
access to P-
Flash
Not possible
Not possible
Data Sheet
20
V1.0, 2010-03