w77e58 Winbond Electronics Corp America, w77e58 Datasheet - Page 75

• Manufacturer Part Number: w77e58
• Description: 8 Bit Microcontroller
• Manufacturer: Winbond Electronics Corp America

B0:Lock bit
This bit is used to protect the customer's program code in the W77E58. 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.
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 Feature
Both the Seed 0 and Seed 1 are a one-byte flash memory cell that provide the user with encryption
code protection. When program code is programmed to the W77E58 internal MTP ROM and verify it
is correct, then users can program a non-FFh value into either Seed 0 or Seed 1 to start the
encryption logic. When Seed 0 or Seed 1 is presented in non-FFh state, the internal encryption circuit
will generate a sequence of random values, then add to each the program code bytes before they
appear in the data bus. Now the code is scrambled during the read or verify operation. The Seed 0
and Seed 1 have the initial value FFh after chip erased. When the encryption logic is effective, the
user can not disable it except by erasing the chip to recover the Seed 0 and 1 to initial value FFh.
The method for programming Seed 0 and Seed 1 is the same as that used to program internal MTP
ROM, except that the address of Seed 0 is 0FF7Fh, and Seed 1 is 0FF3Fh. When B2 bit is cleared,
Seed 0 and Seed 1 can not be accessed.
ABSOLUTE MAXIMUM RATINGS
Note: Exposure to conditions beyond those listed under Absolute Maximum Ratings may adversely affect the life and reliability
DC Power Supply
Input Voltage
Operating Temperature
Storage Temperatute
of the device.
SYMBOL
PARAMETER
V
DD
V
Tst
T
IN
A
V
SS
- 75 -
CONDITION
V
SS
-0.3
-55
0
-0.3
Preliminary W77E58
Publication Release Date: March 1999
RATING
V
DD
+150
+7.0
+70
+0.3
UNIT
Revision A1
V
V
C
C