8

0368H–MICRO–6/08

AT89C2051

To Program and Verify the Array:

4.

Apply data for Code byte at location 000H to P1.0 to P1.7.

5.

Raise RST to 12V to enable programming.

6.

Pulse P3.2 once to program a byte in the PEROM array or the lock bits. The byte-write

cycle is self-timed and typically takes 1.2 ms.

7.

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.

8.

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.

9.

Repeat steps 6 through 8, changing data and advancing the address counter for the

entire 2K bytes array or until the end of the object file is reached.

10. Power-off sequence:

set XTAL1 to “L”

set RST to “L”

Turn V

Data Polling: The AT89C2051 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 writ-

ten 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 PEROM 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 nor-

mal 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) = 21H indicates 89C2051