Intel 8XC251SP Manuale Utente
14-5
PROGRAMMING AND VERIFYING NONVOLATILE MEMORY
Figure 14-1. Setup for Programming and Verifying Nonvolatile Memory
14.4 PROGRAMMING ALGORITHM
The procedure for programming the 87C251Sx is as follows:
1.
Set up the controller for operation in the appropriate mode according to Table 14-1.
2.
Input the 16-bit address on ports 1 and 3.
3.
Input the data byte on port 2.
4.
Raise the voltage on the V
PP
pin from 5 V to 12.75 V.
5.
Pulse the PROG# pin 5 times for the on-chip code memory and the configuration bytes,
and 25 times for the encryption array and the lock bits.
and 25 times for the encryption array and the lock bits.
6.
Reduce the voltage on the V
PP
pin to 5 V.
7.
If the procedure is program/immediate-verify, go to section 14.5, “Verify Algorithm,” and
perform steps 1 through 4 to verify the currently addressed byte. Make sure the voltage on
the EA#/V
perform steps 1 through 4 to verify the currently addressed byte. Make sure the voltage on
the EA#/V
PP
pin has been lowered to 5 V before performing the verifying procedure.
8.
Repeat steps 1 through 7 until all memory locations are programmed.
P0
PSEN#
ALE/PROG#
EA#/V
pp
8XC251S
x
A4122-02
4 MHz
to
6 MHz
XTAL2
A0 - A7
A8 - A15
P3
P1
Data
(8 Bits)
(8 Bits)
V
SS
V
CC
V
CC
XTAL1
Programming
Signals
Signals
Address
(16 Bits)
(16 Bits)
Program/Verify Mode
(8 Bits)
(8 Bits)
P2
RST