saa-xc866 Infineon Technologies Corporation, saa-xc866 Datasheet - Page 28

• Manufacturer Part Number: saa-xc866
• Description: 8-bit Single-chip Microcontroller
• Manufacturer: Infineon Technologies Corporation

3.2.3
The bit protection scheme prevents direct software writing of selected bits (i.e., protected
bits) using the PASSWD register. When the bit field MODE is 11
bit field PASS opens access to writing of all protected bits, and writing 10101
field PASS closes access to writing of all protected bits. Note that access is opened for
maximum 32 CCLKs if the “close access” password is not written. If “open access”
password is written again before the end of 32 CCLK cycles, there will be a recount of
32 CCLK cycles. The protected bits include NDIV, WDTEN, PD, and SD.
PASSWD
Password Register
Field
MODE
PROTECT_S
PASS
Data Sheet
7
Bit Protection Scheme
6
Bits
[1:0]
2
[7:3]
PASS
w
5
Type Description
rw
rh
w
Bit Protection Scheme Control bits
00
11
Others: Scheme Enabled
These two bits cannot be written directly. To change
the value between 11
must be written with 11000
MODE[1:0] be registered.
Bit Protection Signal Status bit
This bit shows the status of the protection.
0
1
Password bits
The Bit Protection Scheme only recognizes three
patterns.
11000
10011
10101
4
Scheme Disabled
Scheme Enabled (default)
Software is able to write to all protected bits.
Software is unable to write to any protected
bits.
B
B
B
24
Enables writing of the bit field MODE.
Opens access to writing of all protected bits.
Closes access to writing of all protected bits.
3
PROTECT
B
and 00
_S
rh
2
B
; only then, will the
Functional Description
B
B
, writing 10011
, the bit field PASS
Reset Value: 07
1
SAA-XC866
MODE
V1.2, 2008-02
rw
B
to the bit
B
0
to the
H