View source for M9302 UNIBUS terminator

[[Image:M9302Terminator.jpg|250px|thumb|right|M9302 terminator card]]

The '''M9302 UNIBUS terminator''' is a [[terminator]] for the [[UNIBUS]]; it provides all three functions of a [[UNIBUS and QBUS termination|UNIBUS terminator]]. The M9302 is a [[DEC card form factor|dual]] format card, intended for use in the [[DEC edge connector contact identification|two top (AB) sections]] of a [[Modified UNIBUS Device|MUD]] slot, or in a UNIBUS in/out slot.

It is a replacement for the original [[M930 UNIBUS terminator]], with so-called 'SACK Turnaround' functionality added.

Note that as a result of the 'SACK Turnaround' circuitry, if there's any break in a [[bus grant line]] (perhaps a missing [[grant continuity card]]) at ''any'' point before it gets to the M9302, the M9302 will jam SACK on (hanging the machine so that it will not run at all; this is fairly easy to recognize and fix). That is because the resulting 'open' input to the [[transistor-transistor logic|TTL]] [[gate]] monitoring the grant line in the device immediately down-stream from the break (perhaps in the M9302) will float high, thereby looking like a permanent incoming grant, which will be turned around by the M9302 as a permanent assertion of SACK. (As mentioned, in many [[PDP-11]] [[Central Processing Unit|CPUs]], that will [[KY11-L to CPU interface|freeze the CPU]].)

==See also==

* [[M8264 No-SACK Timeout Module]]

==External links==

* [http://www.bitsavers.org/pdf/dec/pdp11/1134/MP00082_1134_Vol2_Sep76.pdf 11/34 Vol. 2 Field Maintenance Print Set] - the M9302 is covered on pp. 68-69 of the PDF

[[Category: UNIBUS]]