UNIBUS transceiver was RE: have an extra M105 + M7821 unibus card?
ak6dn at mindspring.com
Sun Feb 5 20:51:40 CST 2006
> From: "Brad Parker"
>> Turns out the RX02 emulator needs an M105 and M7821 single height UNIBUS
>> card to work.
>> Anyone have an extra M105 and M7821?
> I have been looking at suitable driver chips for Unibus/Qbus with Richard,
> and it looks like the SN75ALS057 is both suitable and readily available.
The bus driver/receiver voltage spec (absolute maximum voltage of 2.5V)
of these parts is NOT suitable for UNIBUS/QBUS. These parts are designed
for low voltage swing busses and may work in the short term on UNIBUS,
but will eventually fail, as the UNIBUS termination voltage (static high
level) is 3.5V, 1V over the abs max rating.
I've looked at this problem a bit and the most suitable modern day (ie,
still in active production) part I've found is the Am26S10C. TI now
produces this older AMD part, and it is available in both 16DIP and
16SOIC. It is a quad part not unlike the DS8641. You can get them at
Digikey for about US$1.35 each. Even in Pb-free packages.
The 26S10 has 100ma OC drivers, and the bus receiver input threshold is
in the 1.75-2.25V range, very close to UNIBUS specification. The only
issue I see in using this part is that the specs of the output rise/fall
time are sub 10ns transitions. This may cause problems with reflections,
especially on UNIBUS systems with longer cables.
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