W78LE54C/W78L054C
6. SECURITY BITS
During the on-chip Flash EPROM operation 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 W78L054C has a Special Setting Register, the Security Register, which can not be accessed in
normal mode. The Security 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. The Security Register is addressed in the
Flash EPROM operation mode by address #0FFFFh.
D7 D6 D5 D4 D3 D2 D1 D0
B7
Reserved
B2
B1
B0
Security Bits
16KB Flash EPROM
Program Memory
0000h
B0 : Lock bit, logic 0 : active
B1 : MOVC inhibit,
logic 0 : the MOVC instruction in external memory
cannot access the code in internal memory.
logic 1 : no restriction.
B2 : Encryption
logic 0 : the encryption logic enable
logic 1 : the encryption logic disable
B7 : Osillator Control
logic 0 : 1/2 gain
logic 1 : Full gain
Default 1 for all security bits.
Reserved bits must be kept in logic 1.
3FFFh
Reserved
Security Register
0FFFFh
Special Setting Register
Lock bit
This bit is used to protect the customer's program code in the W78L054C. 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.
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TRIQUINT [ TRIQUINT SEMICONDUCTOR ]
