View source for DA10 Twelve- and Eighteen-Bit Computer Interface

The '''DA10 Twelve- and Eighteen-Bit Computer Interface''' connects [[PDP-10]] [[mainframe]]s to a variety of [[Digital Equipment Corporation|DEC]] [[minicomputer]]s which could be equipped with negative I/O [[bus]]es, for uses such as communication [[front end]]s. These included the 12-bit [[PDP-8 family|PDP-8]], and 18-bit machines such as the [[PDP-9]].

On the PDP-10 side, it connected to the [[PDP-10 I/O Bus]]. Thus, it could be connected to [[KA10]] and [[KI10]] [[Central Processing Unit|CPUs]], but only to [[KL10]]s with the optional [[DIA20 In/Out Bus Controller]] to provide an I/O bus. Unlike the [[DL10 PDP-11 Data Link|DL10]], it didn't use [[Direct Memory Access|DMA]], just [[programmed I/O]]. The device's priority level for [[interrupt]]s is set by a CONO [[instruction]].

The DA10 is used in the DC68A Data Communication System, which uses a [[PDP-8/I]].

==PDP-10 standard instructions==

The device name ('CCI') stands for 'Computer-Computer Interface'. There are a pair of 36-bit [[buffer]] [[register]]s, for input and output (from the -10), which may be read and written with DATI and DATO instructions. The slave minicomputers have means to read/write the top and bottom halves of the buffer registers (for 18-bit slaves), and the three 12-bit segments (for the 12-bit machines).

The interface also has two status bits in each direction:

* From -10 full (which we will call 'F10F')
* From -10 empty ('F10E')
* To -10 full ('T10F')
* To -10 empty ('T10E')

An interrupt is triggered in the -10 by the setting of F10E or T10F; similarly, an interrupt in the slave minicomputer is triggered by the setting of F10F or T10E. 

===CONO CCI===

{{36bithalf-header}}
| colspan=5 | Unused || Disable self-check || Enable self-check || Clear F10F || Set F10F || Clear F10E || Set F10E || Clear T10F || Set T10F || Clear T10E || Set T10E || colspan=3 | Priority interrupt assignment
{{36bithalf-bitout}}

===CONI CCI===
{{36bithalf-header}}
| colspan=6 | Unused || Self-check enabled || Unused || F10F || Unused || F10E || Unused || T10F || Unused || T10E ||  colspan=3 | Priority interrupt assignment
{{36bithalf-bitout}}

==External links==

* [http://bitsavers.org/pdf/dec/pdp10/periph/DEC-10-IACB-D_DA10_PDP8_9_Interface_System_Description_Sep69.pdf DA-10 PDP-8/9 Interface System Description] (DEC-10-IACB-D)
* [http://www.bitsavers.org/www.computer.museum.uq.edu.au/pdf/DEC-10-IACA-D%20DA10%20PDP-8%20&%209%20Interface.pdf DA10 PDP-8/9 Interface Instruction Manual] (DEC-10-IACA-D)
* [http://bitsavers.org/www.computer.museum.uq.edu.au/pdf/DEC-10-XSRMA-A-D%20DECsystem10%20System%20Reference%20Manual.pdf DECsystem-10 System Reference Manual] (DEC-10-XSRMA-A-D) - documents the DA10 on pp. 5-7&mdash;5-12 (pp. 189-194 of the PDF), and the DA10 registers in Appendix C (pg. 357 of the PDF)

[[Category: PDP-10 Machine Interfaces]]