PDP11 PeripheralsHbk 1972 - Trailing-Edge

PART I
Chapter 2
Basic I/O Terminals
2.1 INTRODUCTION
This chapter describes the simplest and most common devices for entering data
to and receiving data from a PDP-ll system: teleprinters, paper tape punches
and readers, line printers and card readers.
The ASR 33 Teletype (DEC model number LT33-DC) is provided as standard
equipment with some basic PDP-ll Family systems. It will type or print information
at a rate of up to'lO characters per second and is equipped with low speed
paper punch and reader (10 cps). A Teletype with keyboard and printer but without
paper tape reader and punch (KSR) is also available. The LA30 DECwriter, a
teleprinter completely designed by DEC, answers the need for a fast reliable, lowcost
terminal and is particularly appropriate for systems requiring large numbers
of highly reliable printer Iterminals. It prints at speeds of up to 30 characters per
second with low noise levels.
The PC11 High Speed Paper Tape Reader and Punch is available for users who
need faster paper tape reading speeds than those offered by the standard ASR 33
Teletype. The PCll reads perforated tape at rates of up to 300 characters per
second and punches tape at 50 characters per second.
The LPll high speed line printer, one of the few line printers available with 80column
width, will print a maximum of 356 full lines per minute (80-column, 64character
model). A 132 column model is also available as are 96 character sets
giving upper and lower case printing.
Any combinations of these devices may be used with a PDP-ll. For example, the
RSTS-ll BASIC-PLUS timesharing system can accommodate up to 16 teleprinter
terminals, in addition to other 1/0 devices.
DEC devices utilize American National Standard Code for Information Interchange
(ANSCII), 1968 version, code.
The eight-bit code used by the Model ASR Teletype is ASCII modified. To convert
ANSCII code to Teletype code, add 200 octal (ASCII + 200. = Teletype). This code
is read in the normal octal form used in the computer. .
On paper tape, bits are numbered from right to left, from 0 through 7, with bits 0
through 2 containing the least significant octal number. H01es corresponding to
bits 2 and 3 are separated by a row of small feed holes for moving the tape.
2.2 TELETYPE
The standard ASR 33 Teletype can be used to type in or print out information, or
to read in or punch out perforated paper tape. Printing, punching and reading are
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