Watlow Series 734 Data Communications - Manual (Page 14)

How to Use Data Communications
14
WATLOW Series 733/734
ANSI X3.28
Table 4 -
Address to ASCII
Conversion.
3 4 0 5
4 ASCII
Characters
HEX Value
4
3 4 0 6
ASCII
Characters
HEX Value
Address ASCII Equivalent
0 - 9 0 - 9
10 - 31 A - V
ANSI X3.28 Protocol for EIA/TIA-422 and EIA/TIA-485
The ANSI X3.28 Protocol provides high quality communications by requiring a
response to every message. With a multiple device or "multidrop" network, this
protocol prevents confusion among the separate devices. Furthermore, if noise
occurs somewhere in the system, no prompt will change because noise can't
comply with the protocol.
By placing messages inside a protocol envelope, the messages are protected. In
the examples to come you'll see how this works.
The ANSI X3.28 Protocol requires STX characters at the beginning of a
message and ETX characters at the end.
Device Address
If you are using the ANSI X3.28 Protocol, you must have a device address (identifi-
cation) number. A Watlow EIA/TIA-422 multidrop network can handle up to 10
devices with this protocol. EIA/TIA-485 can handle up to 32 devices.
Set the address number with the Series 733/734 in the Addr prompt under the
Setup menu.
Starting Communications in ANSI X3.28 Protocol
Here's the syntax for starting communications with ANSI X3.28 Protocol. The
master device, your computer, must initiate the data link. The example below
uses the ASCII number 4 as a Series 733/734 device address.
Enter in ASCII, using this syntax:
Response from the 733/734: