RM0376 Datasheet, PDF (134/968 Pages) STMicroelectronics – This reference manual targets application developers

Firewall (FW)
RM0376
5.4.7
Configuration register (FW_CR)
Address offset: 0x20
Reset value: 0x0000 0000
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
Res. Res. Res. Res. Res. Res. Res. Res. Res. Res. Res. Res. Res. Res. Res. Res.
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Res. Res. Res. Res. Res. Res. Res. Res. Res. Res. Res. Res. Res. VDE VDS FPA
rw
rw
rw
Bits 31:3 Reserved, must be kept at the reset value.
Bit 2 VDE: Volatile data execution
0: Volatile data segment cannot be executed if VDS = 0
1: Volatile data segment is declared executable whatever VDS bit value
When VDS = 1, this bit has no meaning. The Volatile data segment can be executed whatever
the VDE bit value.
If VDS = 1, the code can be executed whatever the Firewall state (opened or closed)
If VDS = 0, the code can only be executed if the Firewall is opened or applying the “call gate”
entry sequence if the Firewall is closed.
Refer to Segment access depending on the Firewall state.
Bit 1 VDS: Volatile data shared
0: Volatile data segment is not shared and cannot be hit by a non protected executable code
when the Firewall is closed. If it is accessed in such a condition, a system reset will be
generated by the Firewall.
1: Volatile data segment is shared with non protected application code. It can be accessed
whatever the Firewall state (opened or closed).
Refer to Segment access depending on the Firewall state.
Bit 0 FPA: Firewall pre arm
0: any code executed outside the protected segment when the Firewall is opened will
generate a system reset.
1: any code executed outside the protected segment will close the Firewall.
Refer to Closing the Firewall.
This register is protected in the same way as the Non-volatile data segment (refer to
Section 5.3.5: Firewall initialization).
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