W78E58B Winbond, W78E58B Datasheet - Page 17

• Manufacturer Part Number: W78E58B
• Description: 8 BIT MICROCONTROLLER
• Manufacturer: Winbond

7. 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 W78E58B 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.
Lock Bit
This bit is used to protect the customer's program code in the W78E58B. 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.
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.
B2: Encryption
B0: Lock bit, logic 0: active
B1: MOVC inhibit,
B07: Osillator Control
Default 1 for all security bits.
Reserved bits must be kept in logic 1.
B7
logic 1: the encryption logic disable
logic 1: no restriction.
logic 0: the encryption logic enable
logic 0: the MOVC instruction in external memory
logic 0: 1/2 gain
logic 1: Full gain
Reserved
cannot access the code in internal memory.
B2
B1
B0
Security Bits
Special Setting Register
- 17 -
Program Memory
4KB On-chip ROM
Security Register
Publication Release Date: March 18, 2002
Reserved
Reserved
LDROM
0000h
0FFFh
FFFFh
7FFFh
32KB On-chip ROM
Program Memory
W78E58B
APROM
Revision A3