IBM 709 General Information Manual page 35

Word Count Address
17 3
Figure 72. Data Channel Registers
Figure 72 shows the format of data channel com-
mands. The operation part of the command is con-
tained in positions S, 1,2, and 19.
The address part, controlling the flow of data, is
contained in positions 21 through 35.
The count part controls the number of words in-
volved in the operation and is located in positions
3 through 17. Position 18 designates indirect address-
ing of the command, in the 7090 system only. Posi-
tion 20 is not used. (Indirect addressing of commands
is available for the 709 as an optional feature.)
As can be seen in Figure 72, the count and address
parts are put into a word count register and an ad-
dress register. The operation parts are put into an
operation register. These registers are, of course, in
the data channel.
Assume that the first command (Figure 71) has an
address part of 3000 and a count part of 00006.
INPUT-OUTPUT, COUNT AND PROCEED (IOCP
00006
3000). This command reads the first six words from
the selected tape and places them into consecutive
core locations starting with location 3000. Each time
a word is moved, the count is reduced by one. When
the count (00006) is reduced to zero, this command
is completed. Because it is a proceed (P) type com-
mand, the next command is brought into the data
channel for execution.
The second command is
INPUT-OUTPUT, COUNT AND
PRO~EED IN NON-TRANSMIT MODE
(IOCPN
00005 0000).
ThIs command results in skipping the next five words
on the same tape. N designates that the five words in-
volved will be read but not placed in core storage
(thus effectively skipping them). Again, because of
the P, the next command is brought into the data
channel.
The third command,
INPUT-OUTPUT UNDER RECORD
CONTROL AND PROCEED (IORP
77777 3006), results in
reading the remainder of the words in that record
into core storage starting with location 3006. Because
the number of words remaining in the record is not
known, the large count (77777) is used. The sensing
of the record gap on the tape signals the end of this
command and the next command is brought into the
data channel (P).
!l4 IBM 709-7090
The fourth command,
INPUT-OUTPUT, COUNT AND
DISCONNECT (IOCD
00000 0000), disconnects or dis-
engages the data channel, thus signaling the central
processing unit that the data channel program is fin-
ished.
A maximum of three data synchronizers (six data
channels) may be used with a 709 system. The data
channels of the first data synchronizer are called A
and B, the second two are C and D, and the third two
are E and F.
Each data channel may have as many as eight
IBM
729 I Magnetic Tape Units attached to it. Data chan-
nels A, C, and E may also have one
IBM
711 Card
Reader, one
IBM
721 Card Punch, and one
IBM
716
Printer attached to each channel. While all data
channels may be operated concurrently with comput-
ing, only one input-output unit per channel may be
in operation at any given time.
A complete 709 Data Processing System is shown
in Figure 73. The additional data synchronizers are
not shown but would be attached in the same manner
as the first.
To summarize the data synchronizer, the word
"channel" is associated with television. Here, a tele-
vision channel might be defined as a band of fre-
quencies over which one station can broadcast sound
. '
pIcture, and pulses to synchronize a receiver with the
camera. If three television stations are broadcasting
simultaneously they must use three separate channels.
A data channel is a group of components that can
transmit data between one input or output device and
core storage and can synchronize the two. If three
1-0
devices are to operate simultaneously, they must use
three separate channels.
A television receiver can receive only one channel
at a time; core storage in a computer can service only
one channel at a time. A television transmitter can
Data Synchronizer Unit
Figure 73.
IBM
709 System