Flash Registers
558
SPRUHE8E – October 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
Internal Memory
5.4.1.9
SECZONEREQUEST Register (SEM) Register
Figure 5-93. SECZONEREQUEST(SEM) Register
31
16
KEY
R/W-0
15
3
2
1
0
KEY
Reserved
SEM
R/W-0
R-0
R/W-0
LEGEND: R/W = Read/Write; R = Read only; -
n
= value after reset
Table 5-101. SECZONEREQUEST(SEM) Register Field Descriptions
Bit
Field
Value
Description
31-4
KEY
Writing the value 0xC12F59A will allow the writing of the SEM bits, else writes are ignored. Reads
will return 0.
Note:
This is to prevent spurious writes of the semaphore bits.
0
1
3-2
Reserved
Reserved
1-0
SEM
Security Zone Semaphore for M3 Flash Wrapper registers
00 or
11
M3 Flash Wrapper registers can be written from code running from anywhere without any restriction
01
M3 Flash Wrapper registers can be written from code running from zone1 security zone
10
M3 Flash Wrapper registers can be written from code running from zone2 security zone
State Transitions
00,11
→
01: code running from zone 1 can perform this transition
01
→
00,11: code running from zone 1 can perform this transition
00,11
→
10 : code running from zone 2 can perform this transition
10
→
00,11 : code running from zone 2 can perform this transition
Notes:
1. In case SEM = “01” writes and reads to the flash registers (including this
register) are blocked if code not in zone1.
2. In case SEM = “10” writes and reads to the flash registers (including this
register) are blocked if code not in zone2.
3. In case SEM = “00/11” writes and reads are not blocked.
4. Debug writes to flash registers (including this register) is blocked if SEM =
01 or SEM = 10
In addition, if sectors belonging to zone1 needs to be programmed or erased then SEM should be
01 or zone1 needs to be unlocked.
Also, if sectors belonging to zone2 needs to be programmed or erased then SEM should be 10 or
zone2 needs to be unlocked.