Programming problem due to capacitance between Vcc and Gnd

[asassler]

Hi. I am doing in-circuit programming of AT25DF321A-SH-T flash memories. Programming the chip out of the circuit is not a problem, but when the chip is in circuit, it sees the decoupling capacitors on all of the 3.3V chips, and this interferes with programming (maybe because the programmer times out while trying to raise the 3.3V line or because it doesn't wait long enough trying to access the chip?). I've gotten the chip to program in-circuit by pulling the ferrite bead to Vcc thus disconnecting the chip from all the rest of the decoupling capacitors.

Questions:
1) Is there any way I can slow things down to allow the prom programmer to pull up the 3.3V supply before starting the programming sequence?
2) If not, how much capacitance can I have between Vcc and Gnd without having a problem? It seems to be OK with 1uF, but fails with 6uF...

Thanks in advance for your help.

Regards,
Alan

[Dataman (Neil Parker)]

Hello Alan,

Which programmer are you using?

Best regards,
Neil Parker
Dataman Programmers