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RM0351 Firewall (FW)
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4 Firewall (FW)
4.1 Introduction
The Firewall is made to protect a specific part of code or data into the Non-Volatile Memory,
and/or to protect the Volatile data into the SRAM 1 from the rest of the code executed
outside the protected area.
4.2 Firewall main features
• The code to protect by the Firewall (Code Segment) may be located in:
– The Flash memory map
– The SRAM 1 memory, if declared as an executable protected area during the
Firewall configuration step.
• The data to protect can be located either
– in the Flash memory (non-volatile data segment)
– in the SRAM 1 memory (volatile data segment)
The software can access these protected areas once the Firewall is opened. The Firewall
can be opened or closed using a mechanism based on “call gate” (Refer to Opening the
Firewall).
The start address of each segment and its respective length must be configured before
enabling the Firewall (Refer to Section 4.3.5: Firewall initialization).
Each illegal access into these protected segments (if the Firewall is enabled) generates a
reset which immediately kills the detected intrusion.
Any DMA access to protected segments is forbidden whatever the Firewall state (opened or
closed). It is considered as an illegal access and generates a reset.
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