23

2601C–MICRO–06/08

AT89LS52

19.1

Serial Programming Algorithm

To program and verify the AT89LS52 in the serial programming mode, the following sequence is

recommended:

1.

Power-up sequence:

a.

Apply power between VCC and GND pins.

b.

Set RST pin to “H”.

If a crystal is not connected across pins XTAL1 and XTAL2, apply a 3 MHz to 16 MHz clock to

XTAL1 pin and wait for at least 10 milliseconds.

2.

Enable serial programming by sending the Programming 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 16.

3.

The Code array is programmed one byte at a time in either the Byte or Page mode. The

write cycle is self-timed and typically takes less than 1 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 device

operation.

Power-off sequence (if needed):

1.

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

2.

Set RST to “L”.

3.

Turn V

Data Polling: The Data Polling feature is also available in the serial mode. In this mode, during

a byte write cycle an attempted read of the last byte written will result in the complement of the

MSB of the serial output byte on MISO.

19.2

Serial Programming Instruction Set

The Instruction Set for Serial Programming follows a 4-byte protocol and is shown in Table 22-1.