Programming interface, Flash programming modes – Rainbow Electronics AT89C4051 User Manual
Page 9
9
AT89C4051
1001D–06/01
3.
Pulse pin XTAL1 once to advance the internal address counter.
4.
Read the next code data byte at the port P1 pins.
5.
Repeat steps 3 and 4 until the entire array is read.
The lock bits cannot be verified directly. Verification of the lock bits is achieved by
observing that their features are enabled.
Chip Erase: The entire PEROM array (4K bytes) and the two Lock Bits are erased elec-
trically by using the proper combination of control signals and by holding P3.2 low for
10 ms. The code array is written with all “1”s in the Chip Erase operation and must be
executed before any non-blank memory byte can be re-programmed.
Reading the Signature Bytes: The signature bytes are read by the same procedure as
a normal verification of locations 000H, 001H, and 002H, except that P3.5 and P3.7
must be pulled to a logic low. The values returned are as follows.
(000H) = 1EH indicates manufactured by Atmel
(001H) = 41H indicates 89C4051
Programming
Interface
Every code byte in the Flash array can be written and the entire array can be erased by
using the appropriate combination of control signals. The write operation cycle is self-
timed and once initiated, will automatically time itself to completion.
All major programming vendors offer worldwide support for the Atmel microcontroller
series. Please contact your local programming vendor for the appropriate software
revision.
Notes:
1. The internal PEROM address counter is reset to 000H on the rising edge of RST and is advanced by a positive pulse at
XTAL1 pin.
2. Chip Erase requires a 10-ms PROG pulse.
3. P3.1 is pulled Low during programming to indicate RDY/BSY.
Flash Programming Modes
Mode
RST/V
PP
P3.2/PROG
P3.3
P3.4
P3.5
P3.7
Write Code Data
12V
L
H
H
H
Read Code Data
H
H
L
L
H
H
Write Lock
Bit - 1
12V
H
H
H
H
Bit - 2
12V
H
H
L
L
Chip Erase
12V
H
L
L
L
Read Signature Byte
H
H
L
L
L
L
(2)