Line Select Sequences; Status Request Sequences - HP 262SA Reference Manual

Data Communications
LINE SELECT.
A CCline select" allows you to select all of the terminals on a communication
line. This is also known as CCBroadcast" mode. Both the group and device ID characters are
replaced with tildes ("-). As with the group select, only a single block ofdata may be sent in each
broadcast and the terminals do not send any response.
Figure 7-15 illustrates the general format ofa line select sequence for both asynchronous and
synchronous configurations.
ASYNCHRONOUS
Line select characters
.
~
"
~
PAD
~ ~
"-
~
\ TEXT
~
Bee PAD
, I
Included in block check
SYNCHRONOUS
Line select characters
, ,
~~~ ~
PAD
~~~ ~ ~ ~ ~
\ TEXT
~
Bee PAD
, I
Included in block check
*Optional
Figure 7-15. Line Select Sequences
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 terminals respond with status information instead of the normal text data. All
terminals in the group that are turned on will send in their status. Figure 7-16 illustrates the
general format of the status request sequence for both asynchronous and synchronous con-
figurations. The right brace character (175 octal) is used in place of the device LD. This tells the
terminal that a status request is being made.
ASYNCHRONOUS
**
~ PAD GROUP ID }} ~ PAD
SYNCHRONOUS
**
~. ~ PAD ~. GROUP ID
GROUP ID }} ~ PAD
*3 or more SYN characters
* *Optional, but if present, should be FF (hex).
Figure 7-16. Status Request Sequences
The Who Are You (WRU) sequence does not destroy any data that is queued up in any of the
terminals. Consequently it is a good way to see if any of the terminals have any data ready to
send.
Three bytes of status information are returned for each responding terminal. Figure 7-17
shows a typical status request and responses from a terminal group.
The status bytes contain terminal hardware and firmware configuration information. The
content of each of the status bytes is explained in figure 7-18. ' )
7-28