AT89 datasheet(26/41 Pages) ATMEL

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AT89S8252

0401F–MICRO–11/03

Serial Programming

Instruction

The Instruction Set for Serial Programming follows a 3-byte protocol and is shown in the

following table:

Notes:

1. DATA polling is used to indicate the end of a byte write cycle which typically takes less than 2.5 ms at 5V.

2. “aaaaa” = high order address.

3. “x” = don’t care.

Instruction Set

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.

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