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4.3 Requests to the DN611
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(b) Polling transmission mode = 1
• The master device checks the polling slave devices for response and makes
a polling request to the individual slave devices in sequence. If there is no
polling response from a slave device, the master device waits for 20 ms
before making a polling request to the next slave device.
• If a slave device does not respond till timeout is repeated three consecutive
times, the slave device is erased from the communicating node list of the
DN611 . This allows the DN611 to continue transmission to the remaining
slave devices in normal operation, without wait time for response.
• Only the slave devices which have failed to respond for three consecutive
timeouts will be erased from the communicating node list. If a slave device
has not responded for two consecutive timeouts but but responded in the
next scan, the number of timeouts for no response is cleared.
• The DN611 periodically checks the slave devices erased from the communi-
cating node list for response and, if any of them responds, it is registered
again on the communicating node list.
• If an n number of slave devices do not respond simultaneously, the real scan
cycle till three consecutive timeouts is as follows:
Real scan cycle = Real scan cycle in normal operation + n number of
slave devices x 20 ms
(6) Bit-strobe slave devices without response
The master device makes a bit-strobe request regardless of whether polling
transmission mode is selected, and waits for bit-strobe response from a slave device
for 20 ms after making the request. After the 20 ms of waiting for response, the
DN611 starts the next scan.
• As long as there is a slave device which does not respond, the master device
waits 20 ms for response every scan.
• The real scan cycle in cases where there is a slave device which does not
respond is expressed as follows:
Real scan cycle = Real scan cycle in normal operation + 20 ms
Usage Recommendations
1. Set a DN611 node address smaller than the node addresses of slave devices (because of the
characteristics of the CAN used for the DeviceNet).
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