AT89C1051U

6

Programming The Flash

The AT89C1051U is shipped with the 1K bytes of on-chip

PEROM code memory array in the erased state (i.e., con-

tents = FFH) and ready to be programmed. The code mem-

ory array is programmed one byte at a time. Once the array

is programmed, to re-program any non-blank byte, the

entire memory array needs to be erased electrically.

Internal Address Counter: The AT89C1051U contains an

internal PEROM address counter which is always reset to

000H on the rising edge of RST and is advanced by apply-

ing a positive going pulse to pin XTAL1.

Programming Algorithm: To program the AT89C1051U,

the following sequence is recommended.

1. Power-up sequence:

Apply power between V

Set RST and XTAL1 to GND

2. Set pin RST to ’H’

Set pin P3.2 to ’H’

3. Apply the appropriate combination of ’H’ or ’L’ logic

levels to pins P3.3, P3.4, P3.5, P3.7 to select one of the

programming operations shown in the PEROM Pro-

gramming Modes table.

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 5 through 8, changing data and advancing

the address counter for the entire 1K-byte 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 AT89C1051U 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 com-

plement 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 indi-

cate 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 (1K 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) = 12H indicates 89C1051U

Programming Interface

Every code byte in the Flash array can be written and the

entire array can be erased by using the appropriate combi-

nation 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.