DeviceNet Network Master/Slave
August 2002 GFK-1539A
3
Bus Connectors and Termination
DeviceNet uses several forms of connectors. The NCM provides the
5-pin standard Phoenix open-style pluggable connector. The pin-to-
signal-to-wire color assignments are shown in the following table:
Pin Signal Wire Color
1V- Black
2 CAN_L Blue
3 Shield Bare
4CAN_HWhite
5V+ Red
Connector orientation on the NCM is shown in figure below:
1 - V-
2 - CAN_L
3 – Shield
4 - CAN_H
5 - V+
Termination of a DeviceNet network is passive and includes one
resistor at each end of the network. A terminating resistor is placed
across the data communication signals at pin 2 (CAN_L) and pin 4
(CAN_H). Correct terminating resistor is a 121 ohm 1% ¼ watt
resistor.
Bus Power Supply and Grounding
DeviceNet requires a power supply of 24VDC (±4%) at a 16A
maximum. However, with the use of Thick cable, a maximum of 8A
is permitted on a single network segment. This is possible if the
power supply is placed at the center point of two network segments,
thus supplying 8A to each segment. With the use of Thin cable, a
maximum of 3A is permitted.
As with most Fieldbus networks, grounding of the network and its
devices is very important. In DeviceNet, it is required that all cable
shields be tied to ground at each device connection. This is done by
tying the bare wire of the cable to pin 3 (Shield) of the connector.
In addition, the DeviceNet network power supply must be grounded,
but only at one point. The V- signal must be connected to Protective
Earth Ground at the power supply only. If multiple power supplies
are used, only one power supply must have V- connected to Earth
Ground.
Configuration Guidelines ________________________
The DeviceNet Network Control Module must be configured in two
steps. The first step uses the configuration software to include the
module in the PLC configuration. The second step uses the
programming software to send a COMMREQ containing the network
addressing and data lengths to the NCM.
PLC Configuration for the DeviceNet NCM
The NCM is configured as part of the overall PLC system
configuration. The configuration software is used to specify the
following module characteristics:
A location. The NCM can be placed in any module location in
the system. In the selected location, insert a Communication
Carrier. On that Carrier, insert a Generic Communications
Module.
Settings:
9Select the Reference Address and Length for an I/O area in
each of the 4 reference types: I, AI, Q, and AQ. The length for
each must exactly match the total amount of data of that type
for all the slave devices controlled by the NCM, including the
64 bits of Communications Status Data provided by the NCM
itself. For example, the %I length must equal the total amount
of all discrete input data contained in the NCM’s input data
area, described later in this chapter. And the %AI length must
equal the total amount of all analog input data contained in
the NCM's input data area. Conversely, the %Q and %AQ
lengths must equal the total amount of all discrete and
analog output data, respectively.
9Enter the Module ID: FFFF9808.
Wiring: can be used to enter tags for the different data points.
Power Consumption: can be used to enter the power consumption
figures for the DeviceNet NCM.
Programming Guidelines ________________________
The second part of configuring an NCM is to send a single COMMREQ
from the application program to the NCM. No communications can
occur until a valid COMMREQ is received by the NCM. The format of
this COMMREQ is shown below.
The configuration COMMREQ defines whether the NCM is used as a
DeviceNet Master, a DevceNet Slave, or as both simultaneously. It
specifies the network address and data rate of the NCM. It also specifies
the network address of each device, the I/O mode, and the lengths of
each slave’s data. The sum of the I/O data for each slave device
(including the NCM itself, if the NCM is a Slave) and the 64 bits of
Communications Status Data must exactly equal the length for each
reference type entered using the configuration software.
Configuring the NCM as a DeviceNet Master Only
When configuring the NCM as a Master, the COMMREQ must specify:
the network address of the Master.
the network data rate of the Master.
For each subordinate slave:
9its network address
9its I/O mode
9the amount of I/O data of each type: I, AI, Q, AQ
Configuring the NCM as a DeviceNet Slave Only
When configuring the NCM as a Slave, the COMMREQ must specify:
the network address
the network data rate
the network mode
the amount of I/O data of each type: I, AI, Q, AQ
Configuring the NCM as a DeviceNet Master and Slave Combined
When configuring the NCM as both a DeviceNet Master and Slave, the
COMMREQ must provide all of the configuration information for both a
Master and Slave. Note that in this combined scenario, the network
mode of the slave is ignored as the Master configuration requires the
slave to be UCMM-capable.
the network address of the Master/Slave.
the network data rate of the Master/Slave.
For the NCM as a Slave the amount of I/O data of each
reference type: I, AI, Q, AQ
For each subordinate slave:
9the network address
9the I/O mode
9the amount of I/O data of each type: I, AI, Q, AQ
