Transmit/Receive Mode (B); Transmit-Transparent/Receive Mode (D); Communications Example - IBM 3742 Reference Manual

If the operator desires to start recording received data from
any position on the first disk, the operator can position
the disk to any record of any data set with normal key
entry operations, and subsequently start receiving and
recording data from that disk position.
If one or two disks of data are received with no errors, an
RC is displayed on the display's status line to indicate a
completed reception of data.
If a disk error occurs or if the disk(s) is full, then RJ will be
displayed on the display's status line. The 3741 will not
automatically answer a telephone call if the mode indicator
indicates RC or RJ. The operator must intervene and
correct or bypass the error condition to continue receiving
data.
If the mode indicator remains R (as it would if a line check,
remote abort, or wrong length check occurred), the 3741
will answer a telephone call and will receive the data begin-
ning at the same place as the original call.
Note:
STX or DLE STX in non-transparent text or DLE
STX (when not immediately preceded by a DLE) in trans-
parent text will be recognized as control characters and
will be deleted from the text. Other BSC products may
not prohibit the transmission of these control characters in
text even though such characters are not supposed to be in
text
Transmit/Receive Mode (B)
The transmit/receive mode of operation is used to transmit
data and receive data without operator intervention. After
loading the disk(s), an operator can place the 3741 in a
transmit/receive mode by pressing FUNCT SEL upper,
COMM, and B. A. B will then be displayed on the display's
status line to indicate the transmit/receive mode.
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 possi-
ble transmission. 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.
For the first received data set, the beginning of extent of
the next label is set to one more than the end of extent of
the last data set transmitted unless the last EOE is equal to
73026. The BOE of disk two is always forced to 01001.
Now data can be received and recorded on the disks on
the same or subsequent telephone call in the same manner
as for the receive mode.
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 indi-
cate a BI 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 indicated in the mode indicator position of the
display's status line. The operator must intervene to cor-
rect or bypass 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 telephone call and will retransmit the data
beginning at the same place as the original call. If the mode
indicator remains BT (as it would if a line check, remote
abort, or wrong length check occurred), the 3741 will
answer a telephone call and will receive the data beginning
at the same place as the original call.
The receiving of data can occur on the same or subsequent
telephone call. The receiving of data can take place on the
same telephone caIJ only when the 3741 is in communica-
tion with a CPU.
Transmit-Transparent/Receive Mode (0)
The transmit-transparent/receive mode of operation is used
to transmit data in the transparent mode and receive data
without operator intervention.
After loading the disk(s), an operator can place the 3741
in a transmit-transparent/receive mode by pressing FUNCT
SEL upper, COMM, and D. A D will then be displayed on
the display's status line to indicate the transmit-transparent/
receive mode.
This mode of operation is identical to the transmit/receive
mode with the exception that data is transmitted in the
transparent mode. DT, DI, DJ, and DC have meanings
corresponding to BT, BI, BJ and BC in the transmit/
receive mode.
COMMUNICATIONS EXAMPLE
Figure 30 iIJustrates the status of a disk on a single disk
drive 3741 Model 2 before teleprocessing is initiated. In
this example, two key-entry data sets are to be transmitted
to the remote CPU and two additional data sets (printer
jobs) are to be received from the CPU. Disk labels 00011
and 00012 have been set up (via bypass status) to be used
for the two printer job data sets.
Communications 57