Watlow PM LEGACY™ Limit Controller  •  10  •  Chapter 1 Overview
PM LEGACY™ Limit PM Models - System Diagram 
(with communications options 2, 3, 5 or 6)
Universal Sensor Input, Configuration Communications, 
Red/Green 7-Segment Display
Note:
  Number of inputs and outputs and various combinations of the same will vary
  depending upon part number; see ordering matrix for more detail.
Output Status 
Indicators
5
6
1
3
2
4
  Zone
Address
Indicators
  Channel
 Indicates Zone 
Address & Channel*
Indicates I/O
Status
* Channel indicator available
  on PM4/8/9 only
Supervisory 
& 
Power 
Board
Slot C
Limit
Controller 
Board 
Slot A
                  Output 2 
      Form A mechanical (5 A) relay
              Output 1 
None, Switched dc/open collector, 
Form C mechanical (5 A) relay
Off, Limit, 
Alarm
EZ-ZONE PM Enhanced Limit Controller System Diagram
with Communications
            Function Key
     Programmable Functions
Digital Output (or Input) 5 & 6
    (optional) None, Switched dc
Off, 
Alarm
              Network
Remote User Interface 
Personal Computer 
Programmable Logic Controller
Human Machine Interface
  EIA 485 Communications 
Standard Bus, Modbus RTU (optional)
Communi-
cations
Board
(optional)
Slot B
            Analog Input 1 
Off, Thermocouple, RTD (100Ω, 1kΩ), 
Thermistor (5kΩ, 10kΩ, 20kΩ, 40kΩ), 
Process (V, mV, mA, 1k potentiometer)
Digital Input (or Output) 5 & 6 
(optional) none, switch, volts dc
None
Limit reset
Loop & alarms off
Silence alarm
Force Alarm
Lock keypad
Restore user settings
Input Sensor
Input
Functions
Output
Functions
         Communications 
EIA-232/485 Modbus RTU, Ethernet/IP, 
DeviceNet, Modbus TCP, Profibus
Limit
Input Events and Output Events
Input events are internal state input event 2. The setting of Digital Input Function (Setup Page, Digital Input/Out-
put Menu) does not change the relationship between the input and the event. An input will still control the input 
event state, even if Digital Input Function is set to None.