W78E365/W78E365A
6.12 Security
During the on-chip ROM programming mode, the ROM can be programmed and verified repeatedly.
Until the code inside the ROM is confirmed OK, the code can be protected. The protection of ROM
and those operations on it are described below.
The W78E365 has a Security Register that can be accessed in programming mode. Those bits of the
Security Registers 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 located at the 0FFFFH of the
LDROM space.
0000h
4KB On-chip ROM
32KB On-chip ROM
Program Memory
Program Memory
Security Bits
B2 B1 B0
LDROM
B7 Reserved
0FFFh
7FFFh
APROM
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.
RReesseerrvveedd
B2: Encryption
logic 0: the encryption logic enable
logic 1: the encryption logic disable
B07: Osillator Control
logic 0: 1/2 gain
FFFFh
Security Register
logic 1: Full gain
Default 1 for all security bits.
Reserved bits must be kept in logic 1.
Special Setting Register
Lock bit
This bit is used to protect the customer's program code in the W78E365. It may be set after the
programmer finishes the programming and verifies sequence. Once this bit is set to logic 0, both the
ROM data and Security 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.
Publication Release Date: January 10, 2007
- 25 -
Revision A9
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