Hi, In one of my design i am using MCP23S17 IC, it is 16 I/O Expander, now i want to interface all pins to ULN2803A IC , Now my question is there any pull up/down resisters required between MCP23S17 AND ULN2803A ?
I had a glance at the datasheet for your driving chip (MCP23S17) and decided to answer in generalities. This would have been so easy to answer if you had used a similar NXP chip (they have '51 style outputs).
The issue here is reset, when the thing is running no pull-up/pull-down will be needed (unless, of course you, for some strange reason, set/configure the driving chip to open collector).
so, if the driving chip has reset connected (I hope you are not using a stupid RC reset), or has an internal reset and the reset state of the outputs is 'good' then no pull-up/pull-down will be needed.
if the driving chip has reset connected, or has an internal reset and the reset state of the outputs is 'bad' you need to redesign.
if the driving chip does not have reset connected you will be in "unknown territory" till the driving processor get up to speed and you need pull-up/pull-down to keep the outputs in the "reset state". BEWARE, if the "self reset" state of the chip leaves outputs driven either high or low and the state of the outputs is 'bad' you need to redesign.
Erik
My computer is running a lenghty operation I have to wait for completion of, thau the unusually long answer.
Erik,
Normally I'd expect people to apologize for short answers due to lack of time ;-)