RE: [BULK] - [IBIS-Users] Input model really needed?

Hi

As I see it, your original buffer is an IO buffer.

Most of our cells are IO buffers, but they are used/connected differently on the die (internally) dependent on, where it is used. I.e. Address bus, data bus, control input etc.

If your basic buffer is an CMOS IO buffer, it can be used/connected internally in the following 8 configurations:
I/O: IO buffer
I/O_open_sink: Input/Open drain output
I/O_open_source: Input/Open source output
3-state: 3-state output buffer
Output: Output (not 3-stateable)
Open_sink: Open drain output
Open_source: Open source output
Input: As pure input buffer

The resulting IBIS model should reflects the buffers use/internal setup, not the basic construction of the buffer.

In your case, I would think that the IO buffer is hardwired internally as a 3-state output or pure output buffer. Make an IBIS model, which reflect that.

When you make the IBIS model, you should off cause include the whole IO buffer in the simulation, but strap the not used parts, so they are passivated.

Regards
/Henrik

-----Original Message-----
From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org]On
Behalf Of Angulo, John
Sent: 11. juni 2004 08:08
To: ibis-users@eda.org
Subject: [BULK] - [IBIS-Users] Input model really needed?

The following is posted on behalf of John Phillippe at Frescale Semiconductor. Please send any private replies to john.phillippe@freescale.com only.

--------------------------

Does anyone know how an IBIS simulator handles an input model? I've got a cmos output buffer that also has an input buffer. The input buffer is identical to the pad being in tristate. So I'm wondering if it is just redundant in this case to include an input model. My thought was that maybe the IBIS tools see the input model, and then allow for some kind of vih/vil measurement to convey logic levels. Are there any reasons that I'm just not seeing?
 

--
John Phillippe
32 Bit Embedded Controller Division, IC Creation
Freescale     -  512-895-1835
Austin, TX    -  john.phillippe@freescale.com
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