4. To verify the programmed data, lower RST from 12V to logic “H” level and set
pins P3.3 to P3.7 to the appropriate levels. Output data can be read at the port
P1 pins.
5. To program a byte at the next address location, pulse XTAL1 pin once to advance
the internal address counter. Apply new data to the port P1 pins.
6. Repeat steps 6 through 8, changing data and advancing the address counter for
the entire 2-Kbyte array or until the end of the object file is reached.
7. Power-off sequence:
set XTAL1 to “L”
set RST to “L”
Turn VCC power off
Data Polling: The AT89C2051x2 features Data Polling to indicate the end of a write
cycle. During a write cycle, an attempted read of the last byte written will result in the
complement of the written data on P1.7. Once the write cycle has been completed, true
data is valid on all outputs, and the next cycle may begin. Data Polling may begin any
time after a write cycle has been initiated.
Ready/Busy: The Progress of byte programming can also be monitored by the
RDY/BSY output signal. Pin P3.1 is pulled low after P3.2 goes High during programming
to indicate BUSY. P3.1 is pulled High again when programming is done to indicate
READY.
Program Verify: If lock bits LB1 and LB2 have not been programmed code data can be
read back via the data lines for verification:
1. Reset the internal address counter to 000H by bringing RST from “L” to “H”.
2. Apply the appropriate control signals for Read Code data and read the output
data at the port P1 pins.
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 program memory array (2K bytes) and the two Lock Bits are
erased electrically 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) = 22H indicates AT89C2051x2
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.
Most worldwide major programming vendors offer support for the Atmel microcontroller
series. Please contact your local programming vendor for the appropriate software
revision.
8
AT89C2051x2
3285B–MICRO–10/03
ATMEL [ ATMEL ]
