Watlow Series 734 Data Communications - Manual (Page 11)

11
WATLOW Series 733/734 How to Use Data Communications
See Syntax
Figure 5 -
Series 733/734
General Message
Syntax Example.
ASCII
Characters
HEX
Value
1
Space
5
0
0
41 4C 31 20 35 30 30
=
3D 20
A
L
0D 4F
O
Example Format
For your benefit, we're presenting message/response examples with syntax
required for Series 733/734 communication. Information bracketed by < > indi-
cates a description, rather than literal characters. We show each ASCII character
that you must transmit to the Series 733/734, including space between the charac-
ters. (A "space" is itself an ASCII character, hex 20). For clarity, we also represent
each ASCII character as a hexadecimal pair. The pairs are spread apart on the
page for easy reading. However, electronic devices "see" the hex pairs all together
in "strings," with no spaces in between.
For instance, from the example just below, you want to set the Alarm 1 Low
(A1LO) prompt to 500°. Notice the syntax just below which uses the "=" command.
= A1LO 500
To send this message, key the ASCII characters into your computer, or write them
into your program. The computer, in turn, will send a string similar to the one at the
bottom of the example, 3D2041314C4F20353030.
Notice that we haven't mentioned protocol here, or any characters added to this
syntax by a protocol. With XON/XOFF, the message above can be transmitted
with only an additional Carriage Return (hex 0D) character at the end. How-
ever, the ANSI X3.28 Protocol requires an envelope of Start of Text (hex
02) and End of Text (hex 03) characters around the information you see
above. You'll learn how to do that in the pages ahead.
XON/XOFF Protocol for EIA/TIA-423
XON/XOFF (flow control) Protocol allows a communicating device (either a 733/
734 or the host) to suspend transmission of all messages from the other device,
and then to continue transmission when it's again ready.
The device that needs to suspend transmission sends the XOFF character
(hex 13) to stop the other device's transmitter, and XON (hex 11) to restart it. Note
that technically any character will restart the transmitter, but only the XON charac-
ter is not a part of any regular message that may be transferring.
Messages transmit according to the syntax described in the XON/XOFF formats
which follow for each command.
The XON/XOFF Protocol requires a Carriage Return character
(hex 0D) at the end of every message.