參數(shù)資料
型號(hào): SAB-C541U-1EP
廠商: SIEMENS A G
元件分類: 微控制器/微處理器
英文描述: 8-Bit CMOS Microcontroller
中文描述: 8-BIT, OTPROM, 12 MHz, MICROCONTROLLER, PDIP52
文件頁(yè)數(shù): 44/65頁(yè)
文件大?。?/td> 427K
代理商: SAB-C541U-1EP
Semiconductor Group
44
1997-10-01
C540U
C541U
Lock Bits Programming / Read
The C540U/C541U has two programmable lock bits which, when programmed according
tabie 11
,
provide four levels of protection for the on-chip OTP code memory. The state of the lock bits can
also be read.
Table 10
Access Modes Selection
Access Mode
EA/
V
PP
PROG
PRD
PMSEL
Address
(Port 2)
Data
(Port 0)
1
0
Program OTP memory byte
V
PP
V
IH
V
PP
V
IH
V
IH
H
H
H
A0-7
A8-15
D0-7
Read OTP memory byte
H
Program OTP lock bits
H
H
L
D1,D0 see
table 11
Read OTP lock bits
H
Read OTP version byte
H
L
H
Byte addr.
of sign. byte
D0-7
Table 11
Lock Bit Protection Types
Lock Bits at D1,D0
Protection
Level
Protection Type
D1
D0
1
1
Level 0
The OTP lock feature is disabled. During normal operation of
the C540U/C541U, the state of the EA pin is not latched on
reset.
1
0
Level 1
During normal operation of the C540U/C541U, MOVC
instructions executed from external program memory are
disabled from fetching code bytes from internal memory. EA is
sampled and latched on reset. An OTP memory read operation
is only possible using the OTP verification mode for protection
level 1. Further programming of the OTP memory is disabled
(reprogramming security).
0
1
Level 2
Same as level 1, but also OTP memory read operation using
OTP verification mode is disabled.
0
0
Level 3
Same as level 2; but additionally external code execution by
setting EA=low during normal operation of the C540U/C541U
is no more possible.
External code execution, which is initiated by an internal
program (e.g. by an internal jump instruction above the ROM
boundary), is still possible.
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