Programming instructions

The CRT, Type 30A is selected when the numbers 0 and 5 (octal) are speci-

fied in bits 8 and 9 respectively, of the iot instruction. The display com-

mands are:

dls - 700506 - Load the Display Buffer and select the display. The program

loads the Display Buffer from the AC. A point is plotted as

specified by the C(Display Buffer). The plotting requires

50 microseconds, after which another dls can be given. The

Light Pen flag or Display flag is cleared with dls.

700502 - Clear the X and Y display buffers. 0 => C(Display Buffer).

700504 - C(AC) V C(Display Buffer)=> C(Display Buffer). Plot the

point specified by the C(Display Buffer).

The points specified in the AC are plotted as unsigned quantities, beginning

in the lower left hand corner of the cathode ray tube. The point locations are:

400377 .

. 377377

--r

2g points

400400 . . 377400 L

A program sequence is given in PDP-4 Assembly language below. The

program begins in register 40, and plots a point, XY, as specified by Core

Memory register 10.

PROGRAM SEQUENCE

/display a point 30a

lO/ , . .

40/ lac 10

/xy bits O-8, bits g-17 y.

/place xy co-ordinate in ac

/display the point, next dls command

/must wait 50 microsec.