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Inputloutput; Introduction; Read Instructions (Rdf) And (Rdr) - RCA Spectra 70 Training Manual

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Table of Contents
INPUT /OUTPUT
INTRODUCTION
The user may elect to control Input/Output by Assem-
bly I/O instructions or by software I/O subroutines.
This section describes the eight Assembly I/O in-
structions, and the methods of error recognition and
recovery.
Up to nine channels connect the RCA 70/25 main-
frame to I/O devices. Each channel has its own
Control Electronics, and is capable of the independent
execution of I/O commands. A feature called MUL-
TIPLEXING makes it possible to connect many
devices, printers, card readers, etc., to a single
channel without the loss of simultaneous capabilities.
CHANNEL 0
I
CONTROL
ELECTROI'HCS
CHANNEL 1
CONTROL
ELECTRONICS
CHANNEL 2
CONTROL
"1
El ECTRONICS
u
~
CHANNEL 3
CONTROL
"-
ELECTRONICS
RCA
~
70/2!J
"1
PROCESSOR
~
CHANNEL 4
CONTROL
ELECTRONICS
q
~
CHANNEL 5
CONTROL
~
~
EI
~
1;;
CHANNEL G
CONTROL
JeT.
CHANNEL 7
I
CONTROL
1
ELECTRONICS
CHANNEL
R
I
CONTROL
MULTIPLEX
ELECTRONICS
I
DE\lCE
I
I
DEVICE
I
I
DEVICf:
I
I
DEVICE
I
I
DEVICE
I
I
DEVICE
I
I
DEVICE
I
I
DEVICE
I
~H
DEVICE
H
DEVICE
4
DEVICE
Up tu FI trunks
on a Multiplex
I
I
I
Two of the eight channels may be used for high-speed
transmission,
and the remaining six for medium
speed, or all eight may be used for the medium speed.
The high-speed channels must be the first two (0 and
1) channels.
To these channels maybe added the ninth channel, a
MULTIPLEX that accommodates up to eight trunks.
The total theoretical data rate available on the 70/25
is 667KB. Because the medium-speed channels and
multiplexor take more time to process each byte than
the high-speed channels, devices operating on the
slower channels must have their peak data rates mul-
tiplied by a weighting factor in the determination of
total equivalent data rate. These weighting factors
are 2.;) for a device operating on a medium-speed
channel, and 4.5 for a device operating in multiplex
mode on the multiplexor channel.
(The multiplexor,
however, cannot exceed a total data rate of ll1KB.)
49
The following configuration is assumed for all ex-
amples in this section.
CHANNEL
UNIT
DEVICE
1
1
1
CARD READER
CARD PUNCH
PRINTER
1
2
3
4
1,2,3,4
TAPE STATIONS
READING DATA
Data is read into High-Speed Memory (HSM) by two
Read Commands. The Read Device Forward can
address all peripheral equipment on line to the sys-
tem. The Read Device Reverse command can be
issued only to tape stations.
READ INSTRUCTIONS
OPERATION
OPERAND
RDF
T(D), D1 (B1)' D2(B2)
RDR
T(D), D1 (B 1 ), D 2 (B2)
These commands select a Channel and Device, and
indicate what HSM area is to receive the data.
Assuming the two HSM areas:
INPT
(HSM 1000-1100)
OUTP (HSM 1200-1319)
The instruction,
OPERATION
OPERAND
RDF
1(1), INPT, INPT + 79
reads a card from the Card Reader (Trunk 1) into
HSM location starting at 1000 (INPT) and ending at
HSM 1079 (INPT+79). Base addresses are implied.
The same instruction with the Trunk number changed:
OPERATION
OPERAND
RDF
4(1), INPT, INPT + 79
reads a block from magnetic tape filling eighty char-
acters of HSM (1000-1079).

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This manual is also suitable for:

Spectra 70/25