Introduction to Data Communications, Chapter 1
Data Communications with the Watlow Series 988 Family
1.7
An Example of a Data Communication Conversation
The computer (the master) initiates an
exchange with controller #2 (the remote).
The computer tells the controller to
change its set point.
The computer queries the controller for
the new set point.
The controller confirms that the new set
point.
The computer ends the session.
computer
2 <ENQ>
(#2, are you there?)
controller
2 <ACK>
(I'm #2, I'm here.)
computer
<STX> = <space> SP1 <space> 500 <return> <ETX>
("Here comes a message."
"Make SP1 = 500
°
."
"I'm done with the message.")
controller
<ACK>
("I understand.")
computer
<STX> ? <space> SP1 <return> <ETX>
("Here comes a message."
"What is SP1 value?"
"I'm done with the message.")
controller
<ACK>
("I understand [the question].")
computer
<EOT>
("That's all, go ahead.")
controller
<STX> 500 <ETX>
( "Here comes the answer."
"The value is 500
°
."
"I'm done with the answer.")
computer
<ACK>
("I understand [the answer].")
controller
<EOT>
("That's all, go ahead.")
computer
<DLE> <EOT> ("Disconnect, please. That's all."
[master waits])
Syntax
