COMMENT ⊗   VALID 00002 PAGES
C REC  PAGE   DESCRIPTION
C00001 00001
C00002 00002	CALCOMP PLOTTER INTERFACE
C00004 ENDMK
C⊗;
CALCOMP PLOTTER INTERFACE

The Calcomp plotter interface is currently located on the P2 TTL
IOB EXT and assigned the device number 344.
The CONO/CONI word has the following format:
____________________________________________
| UNUSED | BUSY | DONE |INTENB| PI CHANNEL |
|18    29|  30  |  31  |  32  |33        35|
|________|____________________|____________|

The DATAO/DATAI word has the following format:
___________________________________________________
|UNUSED|BUSY|DONE| PEN | PEN |CARR |CARR|DRUM|DRUM|
|      |    |    | UP  |DOWN |RIGHT|LEFT|DOWN| UP |
|0   27| 28 | 29 | 30  | 31  | 32  | 33 | 34 | 35 |
|___|____________|_________________|______________|
The busy and done bits are read-only for these instructions.


In general, the operation is as follows.  First, a CONO is
executed, setting INTENB and the PI channel.  Then a DATAO with
the appropriate plotter command.  On receipt of the data, BUSY
is set and DONE is cleared, and the command is sent to the plotter.
After 3.3 milliseconds, BUSY is cleared and DONE is set.  DONE
causes an interrupt if INTENB is set.