w78e516b Winbond Electronics Corp America, w78e516b Datasheet - Page 20

• Manufacturer Part Number: w78e516b
• Description: 8-bit Microcontroller
• Manufacturer: Winbond Electronics Corp America

6. SECURITY
During the on-chip Flash EPROM programming 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 W78E516B has a Special Setting Register, the Security Register, which can not be accessed in
programming 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 located at the 0FFFFH of the LDROM space.
6.1 Lock Bit
This bit is used to protect the customer's program code in the W78E516B. 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 Registers can not be accessed again.
6.2 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.
D7 D6 D5 D4 D3 D2 D1 D0
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
B2: Encryption
logic 1: no restriction.
logic 0: the MOVC instruction in external memory
logic 0: the encryption logic enable
logic 1: the encryption logic disable
Reserved
logic 0: 1/2 gain
logic 1: Full gain
cannot access the code in internal memory.
B2
B1
B0
Security Bits
Special Setting Register
- 20 -
4KB Flash EPROM
Program Memory
Security Register
Reserved
Reserved
LDROM
Publication Release Date: April 22, 2008
0000h
0FFFh
FFFFh
64KB Flash EPROM
Program Memory
W78E516B
APROM
Revision A12