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PRSNT1 & PRSNT2 Signals on backplane
- To: Mailing List Recipients <pci-sig-request@znyx.com>
- Subject: PRSNT1 & PRSNT2 Signals on backplane
- From: Jason Trizna <jbt@mclean.sparta.com>
- Date: Tue, 20 Aug 1996 10:23:23 -0400
- Resent-Date: Tue, 20 Aug 1996 10:23:23 -0400
- Resent-From: pci-sig-request@znyx.com
- Resent-Message-Id: <"sHo-L3.0.dx1.peS6o"@dart>
- Resent-Sender: pci-sig-request@znyx.com
The PCI Specification states that the PRSNT1 and PRSNT2 pins on the 32 bit
PCI connector are related to the connector only:
"They are used for two purposes: indicating that a board is physically
present in the slot and providing information about the total power
requirements of the board." - PCI Spec, Rev. 2.1, Section 4.4.1.
It also states that these signals "inform the motherboard of the power
requirements of the add-in board.... The motherboard provides pull-ups on
these signals to indicate when no board is currently present." Section 2.2.8.
Finally, my question! In a passive backplane, what is done with these pins?
What are they connected to?
The PIC-MG single-board computers (SBC) use these pins for GNT3 and REQ3.
How are the PRSNT pins connected to the SBC to relay the presence of add-in
cards?
Are they not necessary in a passive backplane application?
Regards,
+--------------------------------------------------+
| Jason B. Trizna | Email: jbt@mclean.sparta.com |
| Engineer | Voice: 703 448-1683 x213 |
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U í