Basic Functions; Polling Instruction/Response - Toshiba 2000 V Series Manual

Chapter 1 Overview of the Devicenet Module

1.4 Basic Functions

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1.4.1

Polling instruction/response

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This section describes the following two functions for communication between the DN611
and slave devices.
(1) Polling instruction/response
(2) Bit strobe instruction/response
The polling instruction/response is used for exchanging an arbitrary size of data between
the master device and slave devices.
The master device has information on each slave device on the network (a list of node
addresses, input/output data volume, etc. called the scan list).
With a polling instruction, the master device outputs an arbitrary size of data to a slave
device on the basis of this information.
The slave device transmits response data (of an arbitrary size) in answer to the polling
instruction to the master device. (Polling response). It depends on the specifications of a
slave device how it interprets the polling instruction and what data it transmits as the
polling response.
The slave device must be compatible with the polling instruction/response function in
order for this communication function to be valid. (Most of the DeviceNet slave devices
support this communication function).
(1) Polling Instruction
In the example shown in Figure 1-8, the DN611 receives sensor input information by
polling the sensors, and is about to send output control data to the actuator.
The method of transferring polling output data to the DN611 from the S controller is
described in the text dealing with communication with slave devices in Chapter 5.
S controller
Master
DN611
NA=1
Slave1
proximity sensor
NA=19
Figure 1-8 Example of Polling Instruction/Response
NA (Node address)
Each DeviceNet device connected to a DeviceNet
network has a node address as its identification
number.
The NA range is from 0 to 63 in decimals.
Each device connected to a DeviceNet network must
have a number different from those of the others.
Slave 3
photoelectric sensor
NA=22
Polling instruction/
model 2000 DeviceNet Module Manual (DN611/DN611A)
Slave 5
actuator
NA=52
Polling response