View source for DIA20 IBus Adapter

The '''DIA20 IBus Adapter''' (sometimes called the '''DIA20 In/Out Bus Controller''') is an optional [[device controller|controller]] on [[KL10]] [[Central Processing Unit|CPUs]] which provides an old-style [[PDP-10 I/O Bus]] (termed an 'IBus'), to allow existing [[PDP-10]] [[peripheral]]s to be used on one. Two separate IBuses are provided per CPU. (In a [[multi-processor]] system, each CPU has a separate DIA20, if configured to have one.) Later KL10s did not normally include the backplane into which the DIA20 plugged; that backplane together with a DIA20 were denominated a '''DIB20'''.

==Implementation==

[[Image:KIKLIOBusTerm.jpg|300px|right|thumb|IBus [[terminator]]]]

The DIA20 is connected to the EBox of the KL10 via the EBus; when no other controller on the EBus responds to a command, the DIA20 will respond, and send the command out the IBus. Similarly, [[interrupt]] requests from IBus devices are sent through to the EBox.

It consists of a number of [[DEC card form factor|hex]] boards (two M8550s and an M8551) plugged into an I/O [[backplane]] (one shared with the [[DMA20 Memory Bus Adapter‏‎]]) of the KL10; these are connected to new-style I/O bus connectors mounted lower down in that rack.

==External links==

* [http://www.bitsavers.org/pdf/dec/pdp10/KL10/EK-DIA20-TM-002_Jul76.pdf DIA20 IBus Adapter Unit Description]
* [http://bitsavers.org/pdf/dec/pdp10/KL10/MP00301_KL10PV_Jun80.pdf KL10-PV Field Maintenance Print Set] - Contains DIA20 on pp. 462-487
* [http://www.bitsavers.org/pdf/dec/pdp10/KL10/EK-108OU-PD-002_KL10-Based_Physical_Description_Mar77.pdf KL10-Based Physical Description] - contains images of DIA20 backplanes and wiring, pp. 3-7-3-11; board configuration, pp. 3-27,3-28 

[[Category: PDP-10s]]