RCA 301, Programmer'S Reference Manual

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The Data Exchange Control, Model 377, enables any two 30i Processors, each equipped with this control
to communicate with each other. A second Data Exchange Control may be attached to a 301 Processor when it is
necessary for this Processor to communicate with two other 301 Processors. Data may be transmitted in either
direction but in only one direction at a time. The transfer rate is dependent upon the mode in which the transfer
is made and the availability of status levels in both Processors.
Communications equipment may be included in a system via the Communications Mode Control, Model 378.
A supplementary programmers' reference manual (#93-16-006) is available for use in programming this equipment.
The Videoscan Document Reader, Model 5820, is a high-speed numeric optical character reader which will
read documents of various sizes containing numeric data and/or four special symbols. The data is translated auto­
matically for input to the Processor. The reading rate is either 750 documents per minute or 1500 documents per
minute as determined by a manual switch setting. A supplementary programmers' reference manual (#93-16-004)
is available for use in programming this equipment.
Two additional 301 Processor models are available. The memory capacity is 20,000 (Model 354) or 40,000
(Model 355) alphanumeric characters. In addition to the standard 301 System programming instructions, the
enhanced logic of these processors provide high speed fixed point or floating point arithmetics with associated auto­
matic address modification capabilities. A supplementary programmers' reference manual (#93-16-003) is available
for use in programming this equipment.
Accuracy Control
Adequate accuracy checking techniques are used in the System to assure correct data processing. Correct parity
is ascertained on read-in, during data flow in the Computer, and on write-outs. If a parity error occurs in one of
the Computer modes (Normal, Simultaneous or Data Record File) the mode in which the error occurs is stopped
immediately. The other modes complete their function.
Accuracy of information from the Card Reader and to the Card Punch is assured by use of two separate reading
stations in the Card Reader, and a reading station following the punch unit in the Card Punch. When reading cards
in the Translate Mode of operation, any non-RCA 301 Card Code combination (excluding Y/0) is detected, trans­
ferred into memory as an octal 57 (57
8
), and both the Computer and Card Reader halt after the complete card image
has been transferred to m
A parity check is made of paper tape characters (odd or even input parity) when transferred to the Computer,
and an echo check is made of those characters punched onto paper tape.
With the unbuffered printer, a read error condition (RE) is indicated when the printer table character stored
in the control module for scanning the print field has a parity error. With the buffered printer, RE is indicated for
a parity error on transfer into the buffer.
With the unbuffered printer, a write error condition (WE) is indicated when either of the characters in the diad
sent to the Printer Control module for comparison has a parity error. With the buffered printer, WE indicates
detection of an off-line (printer accessing buffer) parity error. WE indication occurs on the next command to the
printer.
A DDF occurs if the device is inoperable or a line advance or a page change command is received when a low
paper supply exists.
The Data Record File possesses a lock-out feature to prevent writing on a "master" record. An accuracy check
also warns of malfunctioning Block or Character Counter.
The Data Disc File checks if the positioner is in the correct track, and it has a bit counter to assure that the
bit-serial to character-serial conversion is functioning properly. If a character with faulty parity is read, an octal
57 (57
g
) will be stored in memory in place of the faulty character and an indicator will be set which can be sensed
at the termination of the read instruction.
Magnetic Tape accuracy features include end of reel stops, both beginning of tape and end of tape warning,
dual recording, write lockouts, correct parity of data read and read after write accuracy check.
A parity check is performed on data received from the Interrogating Typewriter. When operated as an output
device, an echo check for correct parity is performed between the typewriter and the control module.
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