On Nov 8, 2004, at 12:08 AM, Odendaal Morne wrote:

> at the moment we are using a PIC16F877 (not the low voltage variant)
> in conjunction with two ULN2803 drivers( to invert the signal two 
> times ),
> in order to convert the signal from the PIC to a lower voltage (3V 
> level)
> required by the 3310.

The ULN2803 is a high current darlington driver.  It doesn't source 
current,
and the darlington has a significant voltage drop (though perhaps not 
at the
low current levels needed to drive signals lines.)  It doesn't seem 
surprising
to me that you'd be having problems using them as level converters.

Many low-voltage capable logic families are tolerant of 5V at their 
inputs,
and could potentially be used as level translators.  TI's "Selecting 
the Right
Level Translation Solution" ( 
http://www-s.ti.com/sc/psheets/scea035a/scea035a.pdf) says:

"Devices from the AUC, LVC, LV-A, and AHC families have 
overvoltage-tolerant inputs."

BillW

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