TC1796
System Units (Vol. 1 of 2)
Data Memory Unit
User’s Manual
8-12
V2.0, 2007-07
DMU, V2.0
The Stand-by SRAM Control Register SBRCTR controls the locking and unlocking of the
DMU stand-by memory (SBRAM).
SBRCTR
Stand-by SRAM Control Register
(E0
H
)
Reset Value: 0000 0000
H
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
0
r
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
0
STBSLK
STBULK
STB
LOC
K
r
w
w
rh
Field
Bits
Type Description
STBLOCK
0
rh
Stand-by Lock Flag
Shows the current lock state of the SBRAM.
0
B
SBRAM is locked
1
B
SBRAM is unlocked
STBULK
[3:1]
w
Unlock Stand-by Lock Flag
In order to unlock the SBRAM, three consecutive write
cycles must be written into STBULK with the following
pattern:
1. Write STBULK = 001
B
2. Write STBULK = 011
B
3. Write STBULK = 111
B
During the three consecutive write operations, STBSLK
must be written with 0000
B
. If any bit of STBSLK is set
when writing a non-zero pattern to STBULK, this is
treated as invalid pattern and the SBRAM will not be
unlocked. Reading STBULK always return 000
B
.
STBSLK
[7:4]
w
Set Stand-by Lock Flag
In order to lock the SBRAM, the value 1001
B
must be
written into STBSLK. At the same time, the value 000
B
must be written into STBULK. If any bit of STBULK is
set when writing 1001
B
to STBSLK, this is treated as
invalid pattern and the SBRAM will not be locked.
Reading STBSLK always returns 0000
B
.