Watlow EZ-ZONE PM User Manual
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Watlow EZ-ZONE
®
PM Limit Controller
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Chapter 4 Home Page
Communication Protocols
When using a communications protocol in conjunction with the EZ-ZONE PML there may be two possible
ports (instances) used. Port 1 or instance 1 is always dedicated to Standard Bus communications. This same
instance can also be used for Modbus RTU if ordered. Depending on the controller part number port 2 (in-
stance 2) can be used with Modbus, CIP and Profibus. For further information read through the remainder of
this section.
Modbus RTU & TCP Protocols
All Modbus registers are 16-bits and as displayed in this manual are relative addresses (actual). Some legacy
software packages limit available Modbus registers to 40001 to 49999 (5 digits). Many applications today re-
quire access to all available Modbus registers which range from 400001 to 465535 (6 digits). Watlow controls
support 6 digit Modbus registers. For parameters listed as float notice that only one (low order) of the two
registers is listed, this is true throughout this document. By default the low order word contains the two low
bytes of the 32-bit parameter. As an example, look in the Operations Page for the Analog Input Value. Find
the column identified in the header as Modbus Relative Address and notice that it lists register 360. Because
this parameter is a float it is actually represented by registers 360 (low order bytes) and 361 (high order
bytes). Because the Modbus specification does not dictate which register should be high or low order Watlow
provides the user the ability to swap this order (Setup Page, [Com] Menu) from the default low/high [lohi]
to high/low [hilo].
Note:
With the release of firmware revision 7.00 and above new functions where introduced into the EZ-ZONE
product line. With the introduction of these new functions there was a reorganization of Modbus registers.
Notice in the column identified as Modbus Relative Address the reference to Map 1 and Map 2 registers for
each of the various parameters. To be backwards compatible in your programming use Map 1 registers. To
be able to implement new functions in the Limit when and if they become available use Map 2 registers.
The Data Map [map] for Modbus registers can be changed in the Setup Page under the [Com] Menu.
This setting will apply across the control.
It should also be noted that some of the cells in the Modbus column contain wording pertaining to an offset.
Several parameters in the control contain more than one instance; such as, profiles (4), alarms (4), etc... The
Modbus register shown always represents instance one. Take for an example the Alarm Silence parameter
found in the Setup Page under the Alarm menu. Instance one of Map 1 is shown as address 1490 and +50 is
identified as the offset to the next instance. If there was a desire to read or write to instance 3 simply add
100 to 1490 to find its address, in this case, the instance 3 address for Alarm Silence is 1590.
To learn more about the Modbus protocol point your browser to
Common Industrial Protocol (CIP DeviceNet & Ethernet/IP
Both DeviceNet and EtherNet/IP use open object based programming tools and use the same addressing
scheme. In the following menu pages notice the column header identified as CIP. There you will find the
Class, Instance and Attribute in hexadecimal, (decimal in parenthesis) which makes up the addressing for
both protocols.
Data Types Used with CIP
int
= Signed 16-bit integer
uint
= Signed 16-bit integer
dint
= Signed 32-bits, long
real
= Float, IEEE 754 32-bit
string
= ASCII, 8 bits per character
sint
= Signed 8 bits , byte
To learn more about the DeviceNet and EtherNet/IP protocol point your browser to
.