TD87C51FA-2 View Datasheet(PDF) - Intel

Part Name

Description

Manufacturer

TD87C51FA-2

CHMOS SINGLE-CHIP 8-BIT MICROCONTROLLERS

Intel 

8XC51FX

PROGRAMMING ALGORITHM

Refer to Table 4 and Figures 10 and 11 for address

data and control signals set up To program the

87C51FX the following sequence must be exercised

1 Input the valid address on the address lines

2 Input the appropriate data byte on the data

lines

3 Activate the correct combination of control sig-

nals

4 Raise EA VPP from VCC to 12 75V g0 25V

5 Pulse ALE PROG 5 times for the EPROM ar-

ray and 25 times for the encryption table and

the lock bits

Repeat 1 through 5 changing the address and data

for the entire array or until the end of the object file is

reached

PROGRAM VERIFY

Program verify may be done after each byte or block

of bytes is programmed In either case a complete

verify of the programmed array will ensure reliable

programming of the 87C51FX

The lock bits cannot be directly verified Verification

of the lock bits is done by observing that their fea-

tures are enabled

Figure 11 Programming Signals Waveforms

272322 – 21

ROM and EPROM Lock System

The 87C51FX program lock system when pro-

grammed protects the onboard program against

software piracy

The 83C51FX has a one-level program lock system

and a 64-byte encryption table See line 2 of Table

5 If program protection is desired the user submits

the encryption table with their code and both the

lock-bit and encryption array are programmed by the

factory The encryption array is not available without

the lock bit For the lock bit to be programmed the

user must submit an encryption table The 83C51FA

does not have protection features

The 87C51FX has a 3-level program lock system

and a 64-byte encryption array Since this is an

EPROM device all locations are user-programma-

ble See Table 5

Table 5 Program Lock Bits and the Features

Program Lock Bits

LB1 LB2 LB3

ProtectIon Type

1 U U U No Program Lock features enabled (Code verify will still be encrypted by the

Encryption Array if programmed )

2 P U U MOVC instructions executed from external program memory are disabled from

fetching code bytes from internal memory EA is sampled and latched on Reset and

further programming of the EPROM is disabled

3 P P U Same as 2 also verify is disabled

4 P P P Same as 3 also external execution is disabled

Any other combination of the lock bits is not defined

17

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