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Data Communications
Line Select. A llline select" allows you to select all of the
terminals on a communication line. This is also known as
llBroadcast" mode. Both the group and device ID charac-
ters are replaced with tildes (-).
The status bytes contain terminal hardware and firmware
configuration information. The content of each of the
status bytes is explained in figure 5-16.
ASYNCHRONOUS
Line select characters
I 1 \ \
E P
~ ~ ~ ~
5 TEXT E B P
O A T
TeA
T D
X
xeD
\
I
Included in block check
SYNCHRONOUS
HI
WHO ARE -
YOU GROUP A.
AFTER LAST
}
DEVICE IN
GROUP HAS
SENT STATUS
AA
n------l·~
STX
GID
} FIRST
DID
DEVICE
STATUS BYTES (3)
IN
ETX
GROUP
BCC
PAD
t
1' 1 (
ACK 1
I . ....
-----).~STX
GID
2ND
DID
}TON
STATUS BYTES (3)
DEVICE
ETX
IN
BCC
GROUP
PAD
f
I I I (
ACK
a
'_II(---·"T
Line select characters
I I
\
\
555
E P
555
""-
.".
"'-
.".
5
TEXT E B P
VVV o A VVV
T
T C A
HHH
T D
HHH
X
X C D
\
I
Included in block check
<~)<PAD)<GROUP
ID)<GROUP
ID)<})<})<~)<PAD)
ASYNCHRONOUS
CONFIGURATION STATUS -
WHO ARE YOU
(WRU). The Who Are You (WRU) control sequence is a
status request from the computer to a terminal group.
It
is
similar to a group poll except that the terminal's respond
with status information instead of the normal text data.
All terminals in the group that are turned on will send in
their status. The status request sequence is shown below.
The right brace character (175 octal) is used in place of the
device ID. This tells the terminal that a status request is
be~ng
made.
SYNCHRONOUS
<~.)<~)<PAD)<~.)<GROUP
ID)
<GROUP
ID)<})<})(~)(PAD)
*
3 or more SYN characters
Figure 5-15. Typical Configuration Status Request
and Response Sequence
Three bytes of status information are returned for each
responding terminal. Figure 5-15 shows a typical status
request and responses from a terminal group.
CONFIGURATION PROCEDURE
Mter you have determined the required multipoint set-
tings for your application follow the flowchart given in
figure 5-17.
5-41
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