W79E201 Datasheet, PDF (66/87 Pages) Winbond – 8-BIT MICROCONTROLLER

W79E201
20. SECURITY BITS
Using device programmer, 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 W79E201 has Special Setting Register
which can be accessed by device programmer. The register can only be accessed from the Flash
EPROM operation 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.
Reserved
B3 B2 B1 B0
Security Bits
B3: 0 -> Enable H/W reboot with P4.0
B2: 0 -> Encryption
B1: 0 -> MOVC Inhibuted
B0: 0 -> Data out lock
Default 1 for each bit.
B0: Lock bit
This bit is used to protect the customer's program code in the W79E201. 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.
B1: 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.
B2: 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.
B3: H/W Reboot with P4.0
If this bit is set to logic 0, enable to reboot 4k LD Flash EPROM mode while RST =H and P4.0 = L
state. CPU will start from LD Flash EPROM to update the user’s program
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