Filter
Top Products
6 F 3 B 0 3 6 4
28
1.4 The Basic Functions
This section describes the following two functions for communicating between the DN211 and
slave devices.
1) Polling instruction/response mode
2) Bit strobe instruction/response mode
1.4.1 The Polling Instruction/Response Mode
The polling instruction/response mode is used for exchanging an arbitrary size of data between the
master device ⇔ slave devices. The master device has information on slaves devices (items of
scan list, such as node address, input/output data volume, etc.) on the network.
For polling instructions, based on such information, the master device outputs an arbitrary size of
data to slave devices. Slave devices transmit response data (arbitrary data size) to a polling
instruction to the master device (polling response).
It depends on the specification of a slave device how the slave device interprets the polling
instruction and what data the slave device transmits as the polling response. For this
communication function, it is prerequisite that the slave device supports the polling
instruction/response mode. (Almost all the slave devices on the DeviceNet support this
communication system).
(1) The Polling Instruction
The example in Figure 1.8 indicates the DN211 is polling sensors, inputting sensor input information,
and trying to send output control data to the actuator. How to write polling output data to the
DN211 from the T2/T2E/T2N is found in "5. Communication with Slave Devices."
Slave 3
Optoelectronic sensor
NA = 22
Slave 5
Actuator
NA = 52
Slave 1
Proximity sensor
NA = 19
T2/T2E/T2N
Master
DN211
NA = 1
NA (Node Address):
Node identification number that individual DeviceNet
devices have in the DeviceNet network. The values
range from 0 to 63 in decimal scale.
In the DeviceNet network, the node addresses of the
devices must be unique and different from each other.
Polling responsePolling instruction /
Figure 1.8 Example of Polling Instruction/Response Mode
(2) The Polling Response
A slave device which received a polling instruction transmits an arbitrary size of response data to
the master device. The content of response data varies depending on the specification of the slave
device. The mechanism the T2/T2E/T2N reads polling response data from the DN211 is explained
in"5. Communication with Slave Devices."