AT89LS8252

0850C–MICRO–3/06

20

Instruction Set

Notes:

1. DATA polling is used to indicate the end of a write cycle which typically takes less than 10 ms at 2.7V.

2. “aaaaa” = high order address.

3. “x” = don’t care.

Instruction

Input Format

Operation

Byte 1

Byte 2

Byte 3

Programming Enable

1010 1100

0101 0011

xxxx xxxx

Enable serial programming interface after RST goes

high.

Chip Erase

1010 1100

xxxx x100

xxxx xxxx

Chip erase both 8K & 2K memory arrays.

Read Code Memory

aaaa a001

low addr

xxxx xxxx

Read data from Code memory array at the selected

address. The 5 MSBs of the first byte are the high order

address bits. The low order address bits are in the

second byte. Data are available at pin MISO during the

third byte.

Write Code Memory

aaaa a010

low addr

data in

Write data to Code memory location at selected

address. The address bits are the 5 MSBs of the first

byte together with the second byte.

Read Data Memory

00aa a101

low addr

xxxx xxxx

Read data from Data memory array at selected

address. Data are available at pin MISO during the third

byte.

Write Data Memory

00aa a110

low addr

data in

Write data to Data memory location at selected address.

Write Lock Bits

1010 1100

x x111

xxxx xxxx

Write lock bits.

Set LB1, LB2 or LB3 = “0” to program lock bits.

Serial Programming Algorithm

To program and verify the AT89LS8252 in the serial pro-

gramming mode, the following sequence is recommended:

1.

Power-up sequence:

Set RST pin to “H”.

If a crystal is not connected across pins XTAL1 and

XTAL2, apply a 3 MHz to 12 MHz clock to XTAL1 pin

and wait for at least 10 milliseconds.

2.

Enable serial programming by sending the Pro-

gramming Enable serial instruction to pin MOSI/

P1.5. The frequency of the shift clock supplied at

pin SCK/P1.7 needs to be less than the CPU clock

at XTAL1 divided by 40.

3.

The Code or Data array is programmed one byte at

a time by supplying the address and data together

with the appropriate Write instruction. The selected

memory location is first automatically erased before

new data is written. The write cycle is self-timed and

typically takes less than 2.5 ms at 5V and less than

10 ms at 2.7V.

4.

Any memory location can be verified by using the

Read instruction which returns the content at the

selected address at serial output MISO/P1.6.

5.

At the end of a programming session, RST can be

set low to commence normal operation.

Power-off sequence (if needed):

Set XTAL1 to “L” (if a crystal is not used).

Set RST to “L”.

Serial Programming Instruction

The Instruction Set for Serial Programming follows a 3-byte

protocol and is shown in the following table: