
ML51/ML54/ML56
Sep. 01, 2020
Page
82
of 719
Rev 2.00
ML
51
/ML
54
/ML
5
6 S
E
RI
E
S
TECHNI
CA
L
RE
F
E
R
E
NC
E
M
A
NU
A
L
ML51/M
L54
/M
L56
Series
Tec
hnical Reference
Manual
6.1.2
Security Protection Memory (SPROM)
The security protection memory (SPROM) is used to store instructions for security application. The
SPROM includes 128 bytes at location address FF80H ~ FFFFH and doesn
’t support “whole chip
erase command”. Figure 6.1-2 SPROM Memory Mapping And SPROM Security Mode shows that the
last byte of SPROM (address: FFFFH) is used to identify the SPROM code is non-secured or secured
mode.
0000H
CHPCON[1] BS = 0
APROM
64K bytes
FFFFH
SPROM
FFFFH
FF80H
SPROM
Non-security mode
SPROM
Security mode
FF80H
FFFFH
FFFEH
0xFF
Others
Figure 6.1-2 SPROM Memory Mapping And SPROM Security Mode
(1) SPROM non-secured mode (the last byte is 0xFF). The access behavior of SPROM is the same
with APROM and LDROM. All area can be read by CPU or ISP command, and can be erased and
programmed by ISP command.
(2) SPROM secured mode (the last byte is not 0xFF). In order to conceal SPROM code in secured
mode, CPU only can perform instruction fetch and get data from SPROM when CPU is run at SPROM
area. Otherwise, CPU will get all 00H for data access. In order to protect SPROM, the CPU instruction
fetch will also get zero value when ICE (OCD) port is connected in secured code. At this mode,
SPROM doesn
’t support ISP program, read or erase.