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Comp.Arch.FPGA | Stratix open-drain pins

There are 6 messages in this thread.

You are currently looking at messages 0 to 6.

Stratix open-drain pins - ernie - 2005-07-05 20:05:00

Hi,

Anyone know if I can configure the output pins of a Stratix FPGA to be
open-drain?

I need open-drain outputs to interface with an SMBus slave device.


Thanks,
Ernie
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Re: Stratix open-drain pins - Sylvain Munaut - 2005-07-05 20:13:00

ernie wrote:
> Hi,
> 
> Anyone know if I can configure the output pins of a Stratix FPGA to be
> open-drain?
> 
> I need open-drain outputs to interface with an SMBus slave device.
> 
> 
> Thanks,
> Ernie
> 

I'm no expert in stratix but I guess you can model the output buffer with :


OE ------,
       |\_____ Out
IN ----|/


Just tie IN to GND and use OE as you command signal.


my_od_out <= '0' when my_od_sig else 'Z'.


Maybe there is even weak pull ups so you don't need external ones.



	Sylvain

Re: Stratix open-drain pins - Rob - 2005-07-05 21:53:00

This is a multi-part message in MIME format.

------=_NextPart_000_000D_01C581AB.EC351660
Content-Type: text/plain;
	charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable

Yes, the Stratix device can.  You can also put a weak-pull up on the =
output pin if you wish.

Open-Drain Output

Stratix devices provide an optional open-drain (equivalent to an =
opencollector)

output for each I/O pin. This open-drain output enables the

device to provide system-level control signals (e.g., interrupt and =
writeenable

signals) that can be asserted by any of several devices.

 =20

"ernie" <e...@gmail.com> wrote in message =
news:1...@o13g2000cwo.googlegroups.com...
> Hi,
>=20
> Anyone know if I can configure the output pins of a Stratix FPGA to be
> open-drain?
>=20
> I need open-drain outputs to interface with an SMBus slave device.
>=20
>=20
> Thanks,
> Ernie
>
------=_NextPart_000_000D_01C581AB.EC351660
Content-Type: text/html;
	charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META http-equiv=3DContent-Type content=3D"text/html; =
charset=3Diso-8859-1">
<META content=3D"MSHTML 6.00.2900.2668" name=3DGENERATOR>
<STYLE></STYLE>
</HEAD>
<BODY>
<DIV>
<P class=3DMsoNormal><SPAN style=3D"FONT-SIZE:
12pt"><?xml:namespace =
prefix =3D o ns =3D=20
"urn:schemas-microsoft-com:office:office" /><o:p><FONT face=3DArial
=
size=3D2>Yes,=20
the&nbsp;Stratix device can.&nbsp; You can also put a weak-pull up on =
the output=20
pin if you wish.</FONT></o:p></SPAN></P>
<P class=3DMsoNormal><SPAN style=3D"FONT-SIZE:
12pt"><o:p><B><FONT=20
face=3DHelvetica-Condensed-Bold size=3D2><SPAN=20
style=3D"FONT-WEIGHT: bold; FONT-SIZE: 11pt; FONT-FAMILY: =
Helvetica-Condensed-Bold">Open-Drain=20
Output<o:p></o:p></SPAN></FONT></B></P>
<P class=3DMsoNormal><FONT face=3DPalatino-Roman size=3D1><SPAN=20
style=3D"FONT-SIZE: 9pt; FONT-FAMILY: Palatino-Roman">Stratix devices =
provide an=20
optional open-drain (equivalent to an=20
opencollector)<o:p></o:p></SPAN></FONT></P>
<P class=3DMsoNormal><FONT face=3DPalatino-Roman size=3D1><SPAN=20
style=3D"FONT-SIZE: 9pt; FONT-FAMILY: Palatino-Roman">output for each =
I/O pin.=20
This open-drain output enables
the<o:p></o:p></SPAN></FONT></P>
<P class=3DMsoNormal><FONT face=3DPalatino-Roman size=3D1><SPAN=20
style=3D"FONT-SIZE: 9pt; FONT-FAMILY: Palatino-Roman">device to provide=20
system-level control signals (e.g., interrupt and=20
writeenable<o:p></o:p></SPAN></FONT></P>
<P class=3DMsoNormal><FONT face=3DPalatino-Roman size=3D1><SPAN=20
style=3D"FONT-SIZE: 9pt; FONT-FAMILY: Palatino-Roman">signals) that can =
be=20
asserted by any of several devices.</SPAN></FONT><FONT=20
face=3DHelvetica-Condensed-Bold size=3D2><SPAN=20
style=3D"FONT-SIZE: 10pt; FONT-FAMILY: =
Helvetica-Condensed-Bold"><o:p></o:p></SPAN></FONT></P&
gt;
<P class=3DMsoNormal><FONT face=3D"Times New Roman"
size=3D3><SPAN=20
style=3D"FONT-SIZE: =
12pt"><o:p>&nbsp;</o:p></SPAN></FONT>&nbsp;</o:
p></SPAN></P></DIV>
<DIV><FONT face=3DArial size=3D2>"ernie"
&lt;</FONT><A=20
href=3D"mailto:e...@gmail.com"><FONT face=3DArial=20
size=3D2>e...@gmail.com</FONT></A><FONT face=3DArial
size=3D2>&gt; =
wrote in=20
message </FONT><A=20
href=3D"news:1...@o13g2000cwo.googlegroups.com"><FONT=

=20
face=3DArial=20
size=3D2>news:1...@o13g2000cwo.googlegroups.com</FONT=
></A><FONT=20
face=3DArial size=3D2>...</FONT></DIV><FONT face=3DArial
size=3D2>&gt; =
Hi,<BR>&gt;=20
<BR>&gt; Anyone know if I can configure the output pins of a Stratix =
FPGA to=20
be<BR>&gt; open-drain?<BR>&gt; <BR>&gt; I need open-drain
outputs to =
interface=20
with an SMBus slave device.<BR>&gt; <BR>&gt; <BR>&gt;
Thanks,<BR>&gt;=20
Ernie<BR>&gt;</FONT></BODY></HTML>

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Re: Stratix open-drain pins - ernie - 2005-07-06 13:02:00

Thanks Rob.

How do I tell Quartus that I want a specific pin to be open drain?  Do
I have to do something special?  Or is it automatic and transparent to
the user?


Thanks,
Ernie

Re: Stratix open-drain pins - Mike Treseler - 2005-07-06 13:30:00

ernie wrote:

> How do I tell Quartus that I want a specific pin to be open drain?  Do
> I have to do something special?  Or is it automatic and transparent to
> the user?

It will be inferred automatically from the code
if you write it as Sylvain suggested.

my_od_out <= '0' when my_od_sig = '0' else 'Z';

Picking the pin number for my_od_out
is best done with the Quartus GUI.

        -- Mike Treseler

Re: Stratix open-drain pins - ernie - 2005-07-06 13:49:00

Thanks Mike,

That helps a lot.  I appreciate it!


Cheers,
Ernie