Transparent Operation - 2703 Main Storage Transmitting
Transmitting Station
(Moin Storage Contents)
Moin Storage
Receiving Command fl,f2,h WR n,40,99 WR n + 1 00, 00, 1
byte location Location n J n+ n+ n+ 'f 99, 100, 101 Q Q Q Q Q Q Q Q \\ Q Q Q Q Q Q OLE Q (2 Q Q Q Q \\ Q Q Q Q Q Q OLEETX Transmitted Via
1st Write Command SF enters transparent
mode
[ 100 bytes (Characters)]
byte
count = 0 2nd Write
Command
(Contains
End
Sequence)
byte count = 0 (When detected,
Character Stream thru transmitting SF and over communication facility SF leaves Transparent mode.)
OLESTX Q Q Q Q Q Q Q Q \\ Q Q Q Q Q Q OLEOLE Q Q Q Q Q Q Q \\ Q 6 Q Q Q Q Q OLEETX L Leading character by
across line transmitting
Receiving Station
(Main Storage Con.cnts) (thru receiving station SF and into main storage) SF prior to
transmission Location XI OLESTX Q Q Q Q Q Q Q Q \\ Q Q Q Q Q Q LReCeiVing
,Byte t.ecation x + 100/ tOLE Q Q Q Q Q Q Q \\ Q Q Q Q Q Q Q ETX SF enters
transparent
mode
1 st OLE deleted by
receiving SF prior to storing deleted at SF Q Any transparent bit configuration
Figure 15. Transparent Operation
storage. Before going into text mode, the one­
second timeout is utilized and the timeout condition
is reset every time a new End character, STX or SOH, is detected. If the one-second-timeout condi­
tion is recognized before entry into text mode, the
Search command ends with Channel End, Device
End, and Unit Check status (CSW bits 36, 37, and 38)
and the Timeout bit (sense-bit 7) set to one. While
in text mode, no data is sent to main storage and
the SF monitors all data and responses. The GO Search command ends with Channel End, Devicc
End, and Unit Exception status (CSW bits 36, 37,
and 39) upon recognition of an EOT character, or
with Channel End, Device End, and Unit Check
status (CSW bits 36, 37, and 38) and the Timeout
sense bit (bit 7) set to one if the three-second
timeout occurs after entering text mode.
If the first non-SYN character received as a
response to a Poll command was a master-station
address, the Search command chained to the Poll

command ends normally when the ENQ is detected.
All conditions pertaining to the Read command apply
to the Search command under this circumstance. PROGRAMMING NOTE: No fast-selection operation is permitted
with the Search command.
Address Prepare
This command (Adprep) is used by the tributary
station equipped with the Station-Selection feature.
The Adprep command is a pseudo-Read command in
Address Prepare CON 1 Et fIt f2t f3 I IE I Data Address
o 78 31
Count
32 3940 4748 63
that the SF goes through all the actions of a Read
command, yet does not transfer data to main storage.
When the SF accepts the Adprep, the SF monitors
the receive line, following all data on the line. If
the Adprep command is accepted and character
phase is not established (the SYN pattern has not
been detected), the SF starts a three-second timeout,
during which it must recognize SYN followed by one
of the following three conditions:
a. 2703 Address--If a selection address is
detected, the command will end with Channel End and Device End status (CSW bits 36 and
37), thus allowing chaining to a Read command;
or if the polling address is detected, the
command ends with Channel End, Device End,
and Status Modifier status (CSW bits 36, 37,
and 33 respectively). This allows command
chaining to a Read command other than the
Read command used when the selection address
is detected.
b. Text-Mode Entry--Upon entering into text
mode (as a result of recogni zing STX or SOH), the SF will cease looking for its address until
a new SYN SYN EOT sequence is detected.
The SF monitors the data stream while in text
mode, using the three-second timeout for
recognition of SYN characters ... similar
to the Read command operation, but with the
exception that the Address Prepare command
does not end.
c. End-Character Recognition--The recognition
of a new SYN SYN and an End character will
cause the three-second timeout to be reini­
tiated, and the SF will continue to monitor for
a new SYN SYN and its address or an End
character.
If a timeout occurs or if sync is established when the
Adprep command is issued, the SF looks for a SYN
SYN EOT sequence before any of the preceding
condi tions are sought.
The SF decodes up to three addresses. The
addresses are known as the group address, the poll
address, and the selection address.
The group address is used when a station wishes
to receive a transmission as part of a group of
stations, with one of the group of stations pre­
designated as the responding station.
The poll address is the address of the tributary
station used in a polling operation (transmitting),
while the selection address is used as the address of
the tributary station in a selection operation. Poll This command is a pseudo Write command in that
the SF goes through the actions of a normal Write
command until the ENQ control character is detected
Data Address
o 78 31
Count
32 3940 4748 63
in the data received from main storage. The index
character should always follow ENQ, and this index
will be the first character sent to main storage when
the positive response is received. After the ENQ
has been transmitted to the line, the SF enters
receive mode (however, Channel End and Device
End are not sent to main storage). When in receive
mode, the SF looks for the receipt of character
phase. The following conditions may occur:
a. Ti meout - - Following the trans mi tting of the
ENQ, a three-second timeout is initiated.
At the end of three seconds, if the SF is not in
character phase, the Poll command ends with Channel End, Device End, and Status Modifier
status (CSW bits 36, 37, and 33).
b. Recognition of Character Phase-- Upon receipt
of character phase, the operation ends with Channel End, Device End, and Status Modifier
status if the first non-SYN character following
recognition of character phase is not an EOT character. If the first non -SYN character is
an EOT, the SF retui'ns to transmit mode and
transmits the next character immediately
61