This additional. Features Manual describes the 1620
I/O circuitry as it applies to the IBM 1626-1627. A
complete description of the IBM 1626 Plotter Control
Unit and the IBM 1627 Modell and Model 2 Plotters
is contained in the IBM Customer Engineering Instruc-
tion Reference Manual, Form 227-5721.
The 1626 Control Unit is connected between the
1620 and 1627. As such it accepts 1620 output data
and translates it into appropriate plotter commands.
The 1626 is designed to accept output data in the
paper tape code format. Thus, the 1626 is connected
to the 1620 paper tape punch output channel. This
fact precludes the use of the IBM 1621 in conjunction
with the IBM 1626-1627.
Data from 1620 core storage is transferred serially
(by digit) to the 1626 where it is translated into 1627
commands. These commands are then converted in-
to drawing movements
the 1627 Plotter.
The actual recording is produced by incremental
movement of the pen on the paper surface (y-axis)
and by incremental movement of the paper under the
pen (x-axis). The pen is mounted in a carriage that
travels horizontally across the paper as viewed from
the front of the plotter. The vertical. plotting motion
is achieved by rotation of the pin feed drum, which
also acts as a platen (Figure 1-1).
The drum and the pen carriage are bi-directional;
that is, the paper moves up and down and the pen moves
left and right. Control is also provided to lower the
pen or raise the pen from the paper surface. The pen
remains in the up or down state until directed to change
to the opposite status.
The drum and pen -carriage movements and the
pen status are controlled by digits transferred
1626 Plotter Control Unit by a 1620 output instruction.
Each digit is decoded into a directional signal and re-
layed to the 1627 Plotter. Each signal to the plotter
causes a 1/100" incremental movement of the pen
carriage and/or paper, or pen up or a pen down move-
ment.The motion or action resulting from each digit
in the output record is shown in Figure 1-2.
Figure 1-1. Paper and Pen Motions
The plotter is controlled by the following instructions:
Dump Numerically, Op Code 35
Write Numerically, Op Code 38
Write Alphamerically, Op Code 39
The P-address of the instruction defines the high-
order core storage pOSition of the output record. The
plotter is selected by Q8Q9 digits of 02. Op codes 38
and 39 are terminated
a record mark or a group
mark. Op code 35 is terminated by the output of the
last pOSition of a core storage module (output of data
at address 19999, 39999, or 59999).
Positive or negative numerical characters, in
either one-digit numerical form or two-digit alpha-
meric form may be used in the output record. The
use of other characters can cause either conflicting
commands or no command to be sent to the plotter.
Only the absolute value of the digit is translated as a
plotter command (the sign does not affect the direction
of plotter action. Table
Code 35 is used, there should be no record
marks in the data transmitted to the 1626. Record
marks cause conflicting plotter commands.