Watlow PPC-2000 - Manual (Page 223)

PPC-2000 User’s Guide Chapter 5: LogicPro and Modbus Reference
Doc.# 30002-00 Rev 2.3 Watlow Anafaze 195
Digital I/O Parameters in the Database
Digital I/O parameters determine the state and behavior of
digital inputs and outputs found on the PPC’s Processor,
Digital I/O, Digital Input and Digital Output modules.
State and Logic
The State registers containing the value of the digital I/O point
must be interpreted in terms of the Logic, in order to determine
the physical state of the I/O point.
For example, if the State is 1 and the Logic is 1=On, the
corresponding input or output is on. For a dc digital input this
indicates the input is connected to the power supply common.
For an ac input this indicates the signal is detected. For a
digital output or relay output this indicates the output is
conducting.
Conversely, if the State is 1 and the Logic is 0=On, the
corresponding input or output is off. For an input, this indicates
the field device is an open circuit. For an open collector output,
this indicates the output is an open circuit. For a relay output,
this indicates the output is de-energized.
Accessing Digital I/O Parameters with Modbus
For Digital I/O parameters, the Modbus address offsets
correspond to the digital I/O numbers. See Table 5.33 on page
196 through Table 5.36 on page 199 for a list of the module I/O
numbers corresponding to the digital I/O on the Processor and
Digital I/O modules.
Addresses for digital I/O State, Direction, Logic are relative to the
hardware connection to the corresponding field I/O device. For
example, the PPC-2000 processor module has 48 digital I/O
points with registered addresses 1 to 48. The state of the device
connect to pin 1 on the TB50 is stored at address 03001. The
state of the device connected to pin 2 on the TB50 is stored at
address 03002, and so on.
Table 5.38 on page 200 lists first and last Modbus addresses for
each digital I/O parameter. Use these addresses when
accessing digital I/O parameters with third-party software or
operator interface terminals.