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M451
May. 4, 2018
Page
228
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1006
Rev.2.08
M4
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Register Lock Control Register (SYS_REGLCTL)
Some of the system control registers need to be protected to avoid inadvertent write and disturb the
chip operation. These system control registers are protected after the power-on reset till user to
disable register protection. For user to program these protected registers, a register protection disable
sequence needs to be followed by a special programming. The register protection disable sequence is
writing the data “59h”, “16h” “88h” to the register SYS_REGLCTL address at 0x4000_0100
continuously. Any different data value, different sequence or any other write to other address during
these three data writing will abort the whole sequence.
After the protection is disabled, user can check the protection disable bit at address 0x4000_0100 bit0,
1 is protection disable, and 0 is protection enable. Then user can update the target protected register
value and then write any data to the address “0x4000_0100” to enable register protection.
This register is written to disable/enable register protection and read for the REGLCTL status.
Register
Offset
R/W
Description
Reset Value
SYS_REGLCTL
0x100
R/W
Register Lock Control Register
0x0000_0000
31
30
29
28
27
26
25
24
Reserved
23
22
21
20
19
18
17
16
Reserved
15
14
13
12
11
10
9
8
Reserved
7
6
5
4
3
2
1
0
REGLCTL[7:0]
Bits
Description
[31:16]
Reserved
Reserved.
[7:0]
REGLCTL
Register Lock Control Code (Write Only)
Some registers have write-protection function. Writing these registers have to disable the
protected function by writing the sequence value “59h”, “16h”, “88h” to this field. After this
sequence is completed, the REGLCTL bit will be set to 1 and write-protection registers can
be normal write.
[0]
REGLCTL
Register Lock Control Disable Index (Read Only)
0 = Write-protection Enabled for writing protected registers. Any write to the protected
register is ignored.
1 = Write-protection Disabled for writing protected registers.
The Protected registers are:
SYS_IPRST0
: address 0x4000_0008
SYS_BODCTL
: address 0x4000_0018
SYS_PORCTL
: address 0x4000_0024
SYS_VREFCTL:
address 0x4000_0028
SYS_USBPHY:
address 0x4000_002C
CLK_PWRCTL
: address 0x4000_0200 (bit[6] is not protected for power-down wake-up