Watlow Series 942 Data Communications - Manual (Page 3)

How to Use Data Communications
3
WATLOW Series 942
This manual is a supplement to the Series 942 User's Manual. It is for users
with the data communications option. Use in conjunction with the Series 942
User's Manual.
This is expert user-level material and requires previous experience with
data communications.
Two Serial Hardware Interfaces and
Two Software Protocols
Depending on your units model number, you may have one of two hardware
interfaces:
1)RS-422A for a "multidrop" or (multiple device) network, up to ten devices
total; with 4000 ft. network length limit, or RS-423A (RS-232C compatible) for
one on one communication on a 50 ft. network with a 942 and a host com-
puter (945A-XXXX--B000). They are user selectable via internal switches.
See Page 7.
2)EIA-485 (945A-XXXX-D000) also for a multidrop network, up to 32
addresses total, and with a 4000 ft. network length limit.
There are two protocols available to you. Depending on the type of network
you need, you must use the correct combination of interface and protocol.
We use ANSI X3.28 Protocol, based on ANSI X3.28 - 1976 Subcategories
2.2, and A3, with the RS-422A and EIA-485 interface to run a multiple device
network. We also use XON/XOFF Protocol, a simpler protocol, to run a two
device network with an RS-423A interface. XON/XOFF will also work with the
RS-422A and EIA-485 interface, but the network is limited to two devices (one
computer or printer and a Series 942). XON/XOFF Protocol requires no
responses to messages like the ANSI X3.28 Protocol does. Likewise, ANSI
X3.28 Protocol, which provides a response to every message, will work with
the RS-423 interface. But again you are limited to one Series 942 and a host
computer or printer.
To select which protocol you are going to use, go into the Setup menu and use
the MODE key to advance to the Prot parameter. Select either FULL, for ANSI
X3.28 2.2 - A.3, or On for XON - XOFF.
If you are using ANSI X3.28 Protocol, choose an address number for the
control under the Addr parameter following the Prot parameter. This parame-
ter will only appear if Prot = FULL.
Communications Wiring
To connect your Series 942 to a computer, use the next three pages as a
reference. Your computer hardware manual will provide more detailed serial
port pin information. Also refer to the noise prevention section in Appendix 2 of
the Series 942 User's Manual. In the often noisy environments of industrial
locations, it is important not to take noise isolation lightly.
How to Use Data Communications
with the Watlow Series 942
Data Comm