Preliminary W78E51B
D7 D6 D5 D4 D3 D2 D1 D0
0000h
Company ID (#DAH)
Device ID (#E0H)
Security Bits
1
1
0
1
1
0
1
0
4KB MTP ROM
Program Memory
1
1
1
0
0
0
0
0
0FFFh
Reserved B2 B1 B0
B7
Reserved
B0 : Lock bit, logic 0 : active
B1 : MOVC inhibit,
logic 0 : the MOVC instruction in external memory
cannot access the code in internal memory.
logic 1 : no restriction.
B2 : Encryption
Security Register
0FFFFh
logic 0 : the encryption logic enable
logic 1 : the encryption logic disable
B7 : Osillator Control
logic 0 : 1/2 gain
logic 1 : Full gain
Default 1 for all security bits. Reserved bits must be kept in logic 1.
Special Setting Registers
Lock bit
This bit is used to protect the customer's program code in the W78E51B. It may be set after the
programmer finishes the programming and verifies sequence. Once this bit is set to logic 0, both the
MTP ROM data and Special Setting Registers can not be accessed again.
MOVC Inhibit
This bit is used to restrict the accessible region of the MOVC instruction. It can prevent the MOVC
instruction in external program memory from reading the internal program code. When this bit is set
to logic 0, a MOVC instruction in external program memory space will be able to access code only in
the external memory, not in the internal memory. A MOVC instruction in internal program memory
space will always be able to access the ROM data in both internal and external memory. If this bit is
logic 1, there are no restrictions on the MOVC instruction.
Encryption
This bit is used to enable/disable the encryption logic for code protection. Once encryption feature is
enabled, the data presented on port 0 will be encoded via encryption logic. Only whole chip erase will
reset this bit.
+5V
+5V
V
DD
VDD
P0
PGM DATA
PGM DATA
A0 to A7
P1
P0
P1
A0 to A7
V
V
IL
P3.0
P3.1
P3.2
P3.3
P3.6
P3.7
P3.0
P3.1
P3.2
P3.3
P3.6
P3.7
EA/Vpp
ALE
EA/Vpp
ALE
IL
V
CP
V
CP
V
IL
V
IL
V
IL
V
IL
V
IL
V
IL
V
IL
V
IL
RST
RST
V
IH
V
IH
V
IL
V
IH
V
IH
V
IH
PSEN
P2
V
IH
PSEN
V
IL
X'tal1
X'tal2
Vss
X'tal1
X'tal2
Vss
A8 to A15
A8 to A15
P2
Programming Configuration
Programming Verification
Publication Release Date: December 1998
Revision A1
- 11 -
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