On Jan 22, 13:27, Joe R. wrote:
> I missed the first part of this discussion and I just found this
message
> by chance. However it is NOT TTL, it's DCL according to my 1971
Signetics
> Digital 8000 Series TTl/MSI catalog. Since it's not TTL this catalog
> doesn't have a data sheet for it
> >----- Original Message -----
> >From: "Patrick Finnegan" <pat_at_computer-refuge.org>
> >To: "General Discussion: On-Topic and Off-Topic Posts"
> ><cctalk_at_classiccmp.org>
> >Sent: Wednesday, January 21, 2004 12:10 AM
> >Subject: Re: brew-your-own-unibus boards?
> >
> >
> >> On Tuesday 20 January 2004 18:06, Tony Duell wrote:
> >> > Driver : 8881 (quad 2 input NAND with open collector outputs)
> >>
> >> Does anyone have a spec sheet on the 8881's?
The essential data is in the back of most QBus handbooks, along with
data for 8640 and 8641. 8881 is a quad 2-input NAND bus driver. 8640
is a quad 2-input NOR bus receiver, 8641 is a quad bus transceiver.
The driver outputs are open-collector.
Bus Driver 8881, 8641:
Input high voltage Vih 2.0V min
Input low voltage Vil 0.8V max
Input high current Iih 60uA max [note 6]
Input low current Iih -2.0mA max [note 6]
Output low voltage,
70mA sink Vol 0.8V max [note 1]
Output high leakage
current at 3.5V Ioh 25uA max [notes 1,3]
Propagation delay to
low state Tpdl 25ns max [notes 1,5]
Propagation delay to
high state Tpdh 35ns max [notes 1,5]
1. This is a critical parameter for use on the I/O bus.
All other parameters ar shown for reference only.
2. This is equivalent to being capable of driving 16
unit loads of standard 7400 series TTL integrated
circuits.
3. Current flow is defined as positive if into the
terminal.
4. Conditions of load are 390 ohms to +5V and and 1.6
k ohms in paralel with 15pF to ground for 10ns
min and 50pF for 35ns max.
5. Times are measured from 1.5V level on input to 1.5V
level on output.
6. This is equivalent to 1.25 standard TTL unit loading
of input.
8881 Pinout:
___ ___
| U |
Y1 |1 14| Vcc
A1 |2 13| Y4
B1 |3 12| A4
Y2 |4 11| B4
A2 |5 10| Y3
B2 |6 9| A3
GND |7 8| B3
|_______|
While I was looking up my NatSemi Interface databook, I notice it lists
the DS8640 as an exact replacement for an SP380 (quad 2-input NOR bus
receiver), and an 8T380 is the same thing.
An 8881 is very similar to a 7401. The main difference is that bus
drivers can typically sink 50mA Iol or so at Vol, whereas a 7401 is
only rated for 16mA -- about half what you would expect to need. The
speeds are about the same: 7401 has faster Tpdl (15ns max versus 25ns
max), but slightly slower Tphl (typically 35ns, max 45ns, albeit for a
slightly lower threshold of 1.3V, versus 35ns max for 1.5V thresholds).
--
Pete Peter Turnbull
Network Manager
University of York
Received on Thu Jan 22 2004 - 17:21:34 GMT