W78E516B-24 Winbond, W78E516B-24 Datasheet - Page 12

• Manufacturer Part Number: W78E516B-24
• Description: 8-BIT MICROCONTROLLER
• Manufacturer: Winbond

SECURITY
During the on-chip MTP-ROM programming mode, the MTP-ROM can be programmed and verified
repeatedly. Until the code inside the MTP-ROM is confirmed OK, the code can be protected. The
protection of MTP-ROM and those operations on it are described below.
The W78E516B has several Special Setting Registers, including the Security Register and
Company/Device ID Registers, which can not 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 contents of the Company ID and Device ID registers
have been set in factory. 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 W78E516B. It may be set after the
programmer finishes the programming and verifies sequence. Once this bit is set to logic 0, both the
MTP ROM data and Special Setting Registers 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
Default 1 for all security bits.
D7 D6 D5 D4 D3 D2 D1 D0
B0: Lock bit, logic 0: active
B1: MOVC inhibit,
B07: Osillator Control
Reserved bits must be kept in logic 1.
B7
1 1 0 1 1 0 1 0
0 1 1
logic 0: the encryption logic enable
logic 1: the encryption logic disable
logic 1: no restriction.
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.
0
0 0
B2
B1
1 0
B0
Company ID (#DAH)
Device ID (#62H)
Security Bits
Special Setting Registers
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Program Memory
Security Register
4KB MTP ROM
Reserved
Reserved
LDROM
0000h
FFFFh
0FFFh
64KB MTP ROM
Program Memory
W78E516B
APROM