W78E54C Datasheet, PDF (11/24 Pages) Winbond – 8-BIT MICROCONTROLLER

W78E54C/W78E054C
6. SECURITY BITS
During the on-chip Flash EPROM operation mode, the Flash EPROM can be programmed and
verified repeatedly. Until the code inside the Flash EPROM is confirmed OK, the code can be
protected. The protection of Flash EPROM and those operations on it are described below.
The W78E054C has a Security Register which can not be accessed in normal mode. These registers
can only be accessed from the Flash EPROM operation mode. Those bits of the Security Register can
not be changed once they have been programmed from high to low. They can only be reset through
erase-all operation. The Security Register is addressed in the Flash EPROM operation mode by
address #0FFFFh.
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
6.1 Lock Bit
This bit is used to protect the customer's program code in the W78E054C. 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.
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Publication Release Date: October 3, 2006
Revision A4