Hi guys, we hope for help!!!!!

We work for a technical school project, to realize ISP-Programming between two ATMEL 89S8252. A Delphi application sends bit-Information’s (Added to the Write-Instruction) serial (V24) to the “Programming Controller” and the Programming-Controller flashs the “Target-Controller” with its Port 0 (with external Pull-up-resistors 22k) in the serial Programming Algorithm.

The signals we send look exactly like the Serial Downloading Waveforms in the data sheet. We tried also to give a shorter clock signal while the Instruction-bit is standing for 50us.

We tried to change one data byte in the code-memory of the target, but it works just 80% of all tries, but we don’t know why! So we can never flash a complete hex-file to it.


This is our algorithm at the Target:

1. RST Hi (Here we tried to set this like discribed in the Errata Sheet(glitch-problem)) 2. wait 90ms
3. flash \"Programm Enable\" Instruction
4. send data-bytes together with Write Instruction on HighAdress (aaaaa010) every 90ms 5. RST auf low after 90ms



Timing for every data-bit:

Set Instruction Input Bit (MSB first)
Wait 50us
Set SCK Hi
Wait 50us ( 100us like the Serial Downloading Waveforms in the data sheet.)
Set SCK LO
Wait 50us ( 0us like the Serial Downloading Waveforms in the data sheet. )
Set next Instruction Input Bit
…

Is there something wrong in our System?

Thank you for help!