W77IE58
Publication Release Date: October 20, 2005
- 71 - Revision A5
11. SECURITY BITS
During the on-chip ROM operation mode, the Flash EPROM can be programmed and verified
repeatedly. Until the code inside the ROM is confirmed OK, the code can be protected. The protection
of ROM and those operations on it are described below.
The W77IE58 has several Special Setting Registers, including the Security Register, which can not be
accessed in normal mode. These registers can only be accessed from the ROM 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
ROM operation mode by address #0FFFFh.
B0: Lock bit
This bit is used to protect the customer's program code in the W77IE58. It may be set after the
programmer finishes the programming and verifies sequence. Once this bit is set to logic 0, both the
ROM 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.
