W78ERD2 Datasheet, PDF (56/72 Pages) Winbond – 8-BIT MICROCONTROLLER

W78ERD2
16. OPTION BITS
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.
D7 D6 D5 D4 D3 D2 D1 D0
B7 B6 B5 B4 B3 B2 B1 B0
B0: Lock bit, Logic 0 is active
Option Bits
B1: MOVC Inhibit, Logic 0 is active
B2: Encryption bit, Logic 0 is active
B3: logic 1 is 12 clock per machine cycle
logic 0 is 6 clock per machine cycle
B4: Enable P2.7 and P2.6 as H/W Reboot Function
logic 1: P2.7 and P2.6 are as I/O Function
logic 0: P2.7 and P2.6 are as H/W Reboot Function
B5: Enable P4.3 as H/W Reboot Function
logic 1: P4.3 is as I/O Function
logic 0: P4.3 is as H/W Reboot Function
B6: Reserved (0)
B7: Logic 1: The Crystal Frequency is above 25MHz
Logic 0: The Crystal Frequency is under 25MHz
4KB Flash EPROM
Program Memory
LD Flash EPROM
0000H
0FFFH
Reserved
64KB Flash EPROM
Program Memory
AP Flash EPROM
Security Register FFFFH
Default 1 is for all Security Bits.
The Reserved bit must be kept in logic 1.
Special Setting Register
Lock bit
This bit is used to protect the customer's program code in the W78ERD2. 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.
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.
Oscillator Control
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