W78E54B Datasheet, PDF (11/21 Pages) Winbond – 8-BIT MICROCONTROLLER

W78E54B
0000h
16KB On-chip ROM
Program Memory
B7 Reserved B2 B1 B0
Security Bits
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
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 Register
Reserved
Security Register
3FFFh
0FFFFh
Lock bit
This bit is used to protect the customer's program code in the W78E54B. It may be set after the
programmer finishes the programming and verifies sequence. Once this bit is set to logic 0, both the
Flash EPROM data and Special Setting Register 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.
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Publication Release Date: December 2000
Revision A3