Hi Steve,

> What's your program written in Peter ?

Its written in 8051 assembler, since I use my adaptor:
http://www.specs.de/~danni/tools/isp53/index.htm

I use the following reset routine:
After every power on, RESET was held high for 50ms and normal operation was entered.
To enable programming:
- pin MOSI, SCK and RESET are pulled low for 1ms
- RESET was pulled high for 10ms (like described in the data sheet)
- programming enable command was sent
- programming

Maybe, the main difference can be, that I put MOSI and SCK to low
before the 0-1 transition of RESET.
Its not especially described in the data sheet, but I think, its the only way to implement the "Serial Downloading Waveforms" diagram, which suggest starting with the SPI pins at low level.


I tested the following devices:

AT89S53-24JC date: 9720
AT89S53-24PC date: 9720
AT89S8252-24PC date: 9721
Now the newest devices (bought this year) are dated with 9727. I can check it too.

I programmed the testroutine (mov P1, #0) without setting lock bits.
After the next power on, I always programmed another routine (hello world) and it works also.


Peter