pull up or pull down function description

Martin Gregory (mgregory@asc.sps.mot.com)
Mon, 21 Sep 1998 09:43:03 +0930

Michel Altheimer writes:
>
> we have a pad which is an input pad with on its input a pullup :
> ___
> |
> | | <---- resistor
> |_| |\
> in ____|__________________| \_______ out
> | /
> |/
>
> We did not manage to make a vital model to describe this behaviour.
>
> In verilog the in pin is described as a tri1 wire, so when a Z is put
> on in, the wire is set to a weak 1 by the simulator.
>
> Is there such behaviour possible with vital models ?

You need to use an intermediate node that you evaluate using Resolved,
something like this:

-- Functionality Working Variables...
variable node : std_logic ;
variable out_zd : std_logic ;

begin

-- Functionality...

node := Resolved(('H', in_ipd));

out_zd := VitalBUF(node);

-- Path Delays

VitalPathDelay01 (
OutSignal => out,
OutSignalName => "out",
OutTemp => out_zd,
Mode => PathDelayMode,
Paths => (
0 => (in_ipd'last_event, tpd_in_out, TRUE)
),
GlitchData => out_GlitchData);

Hope this helps.

Martin.

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-- Martin Gregory <mgregory@asc.sps.mot.com> | _--_|\
-- Program Manager, Modelling & Cosimulation Program | / MASC \
-- Motorola Australia Software Centre | \_.-*._/
-- Phone: +61 8 8203 3612, Fax: +61 8 8203 3501 | v
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