Digital I/O Using Implicit Messages

The Guidance Controller supports exchanging digital I/O values via the EtherNet/IP implicit message protocol. Digital input values received from the remote client (PLC) automatically appear in a special range of GPL digital input signals, and a range of GPL digital output signal values are automatically sent to the remote client.

When the remote client first connects to the GPL EtherNet/IP server, it specifies the fixed repetition rate for messages sent to GPL and for message sent by GPL to the PLC or PAC. The GPL server executes once every 10 milliseconds. Therefore transmission rates must be specified as multiples of this period. While transmission rates of 10 milliseconds are permitted, it is suggested that 20 milliseconds or longer be specified to avoid timeout errors if the GPL system becomes heavily loaded.

The Guidance Controller allows up to four simultaneous digital I/O connections with the same or different PLC’s and PAC’s.

Guidance Controller Digital I/O Configuration

Before configuring or attempting to connect a remote client, you should first configure the Guidance Controller. This configuration is accomplished by setting the "EtherNet/IP DIO map" (DataID 592) strings.

Parameter Database ID	Parameter Name	Description /th>
592	EtherNet/IP DIO map: dir, point, count, signal	An array of up to 4 strings allowing configuration of up to 4 digital I/O mappings.

Each string contains 4 comma-delimited fields.

"dir, point, count, signal"

where

dir	This is a keyword indicating the direction of data transfer: T2O for target to origin, or O2T for origin to target. The Guidance Controller is the target, and the remote PLC is the origin, so T2O transmits GPL output signals to a PLC, and O2T receives digital input signals from a PLC.
point	This is the EtherNet/IP point number that will be defined within the PLC or PAC. This may be any numeric value from 100 to 199. This value is used on the remote client when setting up a connection.
count	This is the number of digital I/O signal values (bits) that will be exchanged. Because the GPL server has been designed to transfers data in groups of 32 bits, this number should be 32, 64, or 96.
signal	This is the number of the first GPL digital IO signal that is to be written or read. For T2O points, the signal number should be in the GPL output range, from 101 through 1565. For O2T, the signal number should be in the GPL input range, from 10101 through 11565. Because the GPL server transfers data in groups of 32 bits, the number should be on a 32-bit boundary: nnn01, nnn33, nnn65. These signals are dynamically installed and removed based on whether or not a remote client is connected to these I/O points. If the remote client disconnects or stops sending O2T data, the corresponding GPL signals are removed and an exception occurs if you try to access their values.

Once the Guidance Controller is configured, enable the server operation by setting database parameter 590, EtherNet/IP Enable, to 1, which causes the server to begin responding to client requests.

Remote Client Configuration

The detailed instructions for configuring a remote client (PLC or PAC) will vary depending on the particular client being used, but the general steps are as follows:

Define a Generic Ethernet Device, and specify the Ethernet IP address that you have assigned to the Guidance Controller. Make sure your remote client and Guidance Controller are on the same Ethernet subnet.
If the Guidance Controller is configured and enabled, you should see a device named "Guidance Controller" or “Precise Controller”.
Specify T2O and O2T connection point numbers that match the T2O or O2T connection points you defined in DataID 592.
Specify the connection data size to be consistent with the number of digital IO signals that are being exchanged. Divide the number of bits specified in the Guidance Controller configuration by 8 to get the number of bytes. For example, if you specified 32 bits on the Guidance Controller, specify 4 bytes on the remote client.
Specify the following connection parameters or their equivalents:

Connection period: 10 msec minimum, 20 msec or longer recommended
Connection type: Point to Point or Multicast
Transport Trigger: Cyclic
Keep TCP connection active during connection

At this point, the GPL digital I/O signals corresponding to active connections will be installed and available for use, and your digital I/O data begins to continuously flow between the Guidance Controller and the PLC or PAC.

Digital I/O Configuration Example

Consider the following sample EtherNet/IP digital I/O map definition:

592, 1, 1, 0, "EtherNet/IP DIO map: dir, point, count, signal" = 
       "O2T, 112, 96, 10201", 
       "T2O, 102, 32, 201"

The first string specifies that 96 digital I/O signal values, starting with I/O connection point 112 on the PLC or PAC, are to be continuously sent from the PLC or PAC to a Guidance Controller. On the Guidance Controller, the standard GPL Signal.DIO method can be used to read these values as input signals 10201 through 10296

The second string specifies that 32 digital I/O signal values, starting with GPL output signal number 201, are to be continuously sent from a Guidance Controller to the PLC or PAC. On the PLC or PAC, these values will appear starting at connection point 102. On the Guidance Controller, the standard GPL Signal.DIO method can be used to set these values as digital output signals 201 through 232.