10
model 3000 DeviceNet Module Manual (DN311/DN311A)
Chapter 1 Overview of the Devicenet Module
1
(2) Bit Strobe Response
As a slave device receives a bit strobe instruction, it transmits response data of 0 to 8
bytes to the master device. Response data varies depending on the specifications of
the slave device.
The way the S controller reads bit strobe response data from the DN311 is described
in the text dealing with communication with slave devices in Chapter 5.
1.4.3
Synchronous/asynchronous mode and data refresh cycle
As explained in the preceding section, there are two functions of communication between
the DN311 and slave devices: polling instruction/response and bit strobe instruction/
response. Data can be exchanged between the S controller and the DN311 in
synchronous mode or asynchronous mode as described below.
(1) Synchronous mode
Output : The S controller writes output data to slave devices into the DN311 in
advance, and activates a polling instruction/bit strobe instruction.
When the polling instruction/bit strobe instruction is activated, the DN311
sends the output data to the slave devices.
Input : The DN311 receives data from slave devices by a polling response/bit
strobe response. After having received data from all the slave devices, the
DN311 processes the input data, then notifies the S controller of input
completion.
For the S controller to read input data, it confirms the input completion from
the DN311, then reads the input data.
Figure 1-10 Data Transfer in Synchronous Mode
Output and input data are exchanged between the S controller and the DN311 in
synchronization with the output/input cycles of the S controller program.
Therefore, only one transfer of output data/input data to or from all the slave devices is
guaranteed as synchronized.
Output
data
Input
data
Output
data
S controller data refresh cycle
S controller
Output
processing
Input
processing
Output
ordered
Input
completion
Output
processing
Input
processing
Output
ordered
Input
completion
DN311
Response
Response
Slave
