Hi all,

I use a CPLD to generate interrupt in a PC104 system. It work's fine.
The question is:
is correct connect CPLD output diretly to PC104 IRQ input (i don't need
interrupt sharing)? Or i need other hardware (pull-up resistor or other)  ?

Thank's in advance

Max

Max wrote:

> Hi all,
> 
> I use a CPLD to generate interrupt in a PC104 system. It work's fine.
> The question is:
> is correct connect CPLD output diretly to PC104 IRQ input (i don't need
> interrupt sharing)? Or i need other hardware (pull-up resistor or other)  ?
> 
> Thank's in advance
> 
> Max
> 
> 

Maybe you don't to need to share at this time, but what for the future !

Your interrupt signal schould be driven by an open-drain and an pull-up.

Depending on your CPLD family, you can map internal pull-up. But if you 
have place on the pcb, please add the pattern for an external pull-up.

In your VHDL, you have :

irq_out <= '0' WHEN an_condition ELSE '1' ;

for an open-drain, you just have to change by

irq_out <= '0' WHEN an_condition ELSE 'Z' ;
   -- you need here an pull-up to fix '1';

Regards,
Laurent Gauch
www.amontec.com

Max wrote:

> I use a CPLD to generate interrupt in a PC104 system. It work's fine.
> The question is:
> is correct connect CPLD output diretly to PC104 IRQ input (i don't
> need interrupt sharing)? Or i need other hardware (pull-up resistor
> or other)  ?

Hello Max,

No, you don't need other hardware.  No resistors, no open-collector outputs.

Karl Olsen

laurent gauch wrote:
> 
> Max wrote:
> 
> > Hi all,
> >
> > I use a CPLD to generate interrupt in a PC104 system. It work's fine.
> > The question is:
> > is correct connect CPLD output diretly to PC104 IRQ input (i don't need
> > interrupt sharing)? Or i need other hardware (pull-up resistor or other)  ?
> >
> > Thank's in advance
> >
> > Max
> >
> >
> 
> Maybe you don't to need to share at this time, but what for the future !
> 
> Your interrupt signal schould be driven by an open-drain and an pull-up.
> 
> Depending on your CPLD family, you can map internal pull-up. But if you
> have place on the pcb, please add the pattern for an external pull-up.
> 
> In your VHDL, you have :
> 
> irq_out <= '0' WHEN an_condition ELSE '1' ;
> 
> for an open-drain, you just have to change by
> 
> irq_out <= '0' WHEN an_condition ELSE 'Z' ;
>    -- you need here an pull-up to fix '1';

Time out Laurent!  This is exactly wrong.  The IRQ is an active *HIGH*
signal.  So you have to drive the signal high when asserted, hi-z when
not asserted and use a pull-down resistor as the common element to
assert a low on an open bus.  


-- 

Rick "rickman" Collins

r...@XYarius.com
Ignore the reply address. To email me use the above address with the XY
removed.

Arius - A Signal Processing Solutions Company
Specializing in DSP and FPGA design      URL http://www.arius.com
4 King Ave                               301-682-7772 Voice
Frederick, MD 21701-3110                 301-682-7666 FAX

I'm also trying to design a PC104 (ISA) bus board.
I will interface an ADC and FIFO buffer to PC104 (ISA) bus.
I need to control ADC to digitize input signal in a burst and store the
converted data into a FIFO.
When FIFO is full, I need to generate an interrupt to signal the PC104 for
data transfer.
Unfortunatelly I do not have experience with CPLDs (yet).
Is it possible if you can share your CPLD design with us so that we can
learn from your experience?

Regards,


> Hi all,
>
> I use a CPLD to generate interrupt in a PC104 system. It work's fine.
> The question is:
> is correct connect CPLD output diretly to PC104 IRQ input (i don't need
> interrupt sharing)? Or i need other hardware (pull-up resistor or other)
?
>
> Thank's in advance
>
> Max
>
>

"k" <k...@k.com> ha scritto nel messaggio
news:4062da30$0$25292$a...@news.optusnet.com.au...
> I'm also trying to design a PC104 (ISA) bus board.
> I will interface an ADC and FIFO buffer to PC104 (ISA) bus.
> I need to control ADC to digitize input signal in a burst and store the
> converted data into a FIFO.
> When FIFO is full, I need to generate an interrupt to signal the PC104 for
> data transfer.
> Unfortunatelly I do not have experience with CPLDs (yet).
> Is it possible if you can share your CPLD design with us so that we can
> learn from your experience?
>
> Regards,


Hi,
my board will interface a Philips SJA1000 CAN controller to PC104 bus;
CPLD is used first af all to make other things (address docode for other
chip, clock divider,ecc...).
I need to invert SJA1000 INT line and connect it to PC 104 IRQ line so i use
a gate of the CPLD (...but in the same way i can use a 74HC04: i think that
my experience will not help you....)


Regards,

Max