IBM 3741 Data Station Reference Manual page 81

The 3741 can then be connected to the telephone line
through a modem. When the connection has been made!
data will be transmitted beginning with the first disk until
all index positions of disk one have been interrogated for
possible transmission. Only valid (HOR 1) data set labels
can be transmitted. Valid (HOR 1) data set labels with a
B (bypass) in position 41 are not transmitted. Data set
labels that are deleted or invalid are not transmitted. A
C in the multivolume indicator will allow transmitting
the continuation of the data set on disk two. A BT is
indicated in the mode indicator position on the display's
status line indicating a completed transmission. The
transmit/receive mode then switches to receive. Data is
received into the first data set whose label qualifies for
receiving data. For disk 1, a label qualifies for receiving
data if it is a valid HO R 1 label, has a B in the bypass field,
and is after the last transmitted data set. For disk 2, a
label qualifies for receiving data if it is a valid HOR1 label
or a HOR1 label with a B in the bypass field.
For the first data set to be received, the beginning of extent
of the data set's label is set to one more than the end of
extent of the last data set transmitted unless the last EOE
address is equal to 73026.
To transmit disk 1 and receive on disk 2, set EOE of the
last data set transmitted on disk 1 to 73026.
The BOE of the first data set label on disk 2 is set to
01001 if transmission ends on disk 1.
Data can be received and recorded on the disks in the same
or subsequent telephone call. (See Figure 39 for a summary
of extents generated during the receive portion of the
transmit/receive mode.)
BOE EOO
When the 3741 has received all of the data transmitted to
it, it will display BC to indicate a completed transmission
and reception of data.
If a disk error or a transparency error has occurred during
the transmission portion of this mode, the 3741 will indicate
a B I in the mode indicator position of the display's status
line. If a disk error or a disk full condition occurs during
the receive portion of this mode of operation, a BJ is in-
dicated in the mode indicator position of the display's
status line. The operator must intervene to correct or by-
pass the error condition.
If the mode indicator remains B (as it would if a line check,
remote abort, or message aborted error occurred), the 3741
will answer a phone call and will transmit the data beginning
at the same place as the original call. However, on early
shipments of the 3741 Model 2, if communications mode
was selected with a data set record displayed, the operator
must reposition the disk to the original starting position.
Your 3741 can be field upgraded so that the operator does
not have to reposition the disk to the original starting posi-
tion. Contact your IBM representative for more informa-
tion. If your 3741 has not been field upgraded and you
are performing unattended operations, it is recommended
that the communications mode be selected while the label
is displayed. If the mode indicator remains BT (as it would
if a line check, remote abort, or wrong length check oc-
curred), the 3741 will answer a telephone call and will re-
ceive the data beginning at the receive mode start point.
The receiving of data can occur on the same or subsequent
telephone call. The receiving of data can take place on the
same telephone call only when the 3741 is in communica-
tion with a CPU.
EOE
Succeeding data sets on Previous EOO
BOE
+
number of EOO - 1 (if null data
first or second disk records received
set, EOO)
First data set following a Previous EOE
+
1 BOE
+
number of EOO - 1 (if null data
transmitted data set on records received set, EOO)
first or second disk.
First received data set on
01001 BOE
+
number of EOO - 1 (if null data
second disk if the transmit
records received
set, EOO)
ended on disk 1.
Figure 39. Generated Extents while in Receive Portion of the Transmit/Receive Mode
Communications 75