DA10 Twelve- and Eighteen-Bit Computer Interface

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The DA10 Twelve- and Eighteen-Bit Computer Interface connects PDP-10 mainframes to a variety of DEC minicomputers which could be equipped with negative I/O buses, for uses such as communication front ends. These included the 12-bit PDP-8, and 18-bit machines such as the PDP-9.

On the PDP-10 side, it connected to the I/O bus. Thus, it could be connected to KA10 and KI10 CPUs, but only to KL10s with the optional DIA20 In/Out Bus Controller to provide an I/O bus. Unlike the DL10, it didn't use DMA, just programmed I/O. The device's priority level for interrupts 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 registers, 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

Unused Disable self-check Enable self-check Clear F10F Set F10F Clear F10E Set F10E Clear T10F Set T10F Clear T10E Set T10E Priority interrupt assignment
18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35

CONI CCI

Unused Self-check enabled Unused F10F Unused F10E Unused T10F Unused T10E Priority interrupt assignment
18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35