Configuration Register (Fw_Cr) - ST STM32L4x6 Reference Manual

RM0351
4.4.7

Configuration register (FW_CR)

Address offset: 0x20
Reset value: 0x0000 0000
31 30 29
Res. Res. Res. Res.
15 14 13
Res. Res. Res. Res.
Bits 31:3 Reserved, must be kept at the reset value.
Bit 2 VDE: Volatile data execution
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
Bit 1 VDS: Volatile data shared
Refer to
Bit 0 FPA: Firewall pre arm
Refer to
This register is protected in the same way as the Non-volatile data segment (refer to
Section 4.3.5: Firewall
28 27 26 25
Res. Res. Res.
12 11 10 9
Res. Res. Res.
0: Volatile data segment cannot be executed if VDS = 0
1: Volatile data segment is declared executable whatever VDS bit value
Segment access depending on the Firewall
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).
Segment access depending on the Firewall
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.
Closing the Firewall.
initialization)
24 23 22
Res. Res. Res.
8 7 6
Res. Res. Res.
.
DocID024597 Rev 3
21 20 19 18
Res. Res. Res. Res.
5 4 3 2
Res. Res. Res. VDE
rw
state.
state.
Firewall (FW)
17 16
Res. Res.
1 0
VDS FPA
rw rw
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