Polling scheme in an industrial network system
For polling communication devices in a communication system including a host device and communication devices. The host device is connected to the communication devices via a clock line for transmitting a clock signal to the communication devices and via an arbitration line implemented with “AND” logic for receiving arbitration signal transmitted by the communication devices. Each communication device is associated with an address. Each communication device is configured to pull up or down the arbitration line for sending an arbitration signal according to the associated address when the communication device is ready to send data to the host device. The host device is able to: send a clock signal on the clock line during an arbitration cycle, causing the communication devices to send respective arbitration signals towards the arbitration line according to respective associated addresses from highest bit to lowest bit, during the arbitration cycle, receive a final signal corresponding to the lowest address, during the arbitration cycle, resulting from the “AND” logic applied to the arbitration signals, select the communication device associated with the lowest address, and poll the selected communication device to receive data from the selected communication device during a communication cycle.
1 . A method for polling communication devices in a communication system comprising a host device and the communication devices, wherein the host device is connected to the communication devices via a clock line for transmitting a clock signal to the communication devices and via an arbitration line implemented with “AND” logic for receiving arbitration signals transmitted by the communication devices, wherein each communication device is associated with an address, wherein each communication device is configured to pull up or down the arbitration line for sending an arbitration signal according to the associated address when the communication device is ready to send data to the host device, the method comprising:
the host device sending a clock signal on the clock line during an arbitration cycle;
the communication devices sending respective arbitration signals towards the arbitration line according to respective associated addresses from highest bit to lowest bit, during the arbitration cycle;
the host module device receiving a final signal corresponding to a lowest address of the associated addresses, during the arbitration cycle, resulting from the “AND” logic applied to the arbitration signals;
the host device selecting a communication device of the communication devices associated with the lowest address; and
the host device polling the selected communication device to receive data from the selected communication device during a communication cycle.
2 . The method according to claim 1 , wherein when a selected communication device has sent data to the host device, the selected communication device does not send an arbitration signal during a next arbitration cycle.
3 . The method according to claim 1 , wherein at each clock period of the clock signal, a communication device readbacks a value of the final signal, and when the readback value is different from a value of the arbitration signal sent by the communication device, the communication device stops sending an arbitration signal during the arbitration cycle.
4 . The method according to claim 1 , wherein the address associated with a communication device is defined according to a priority between the communication devices.
5 . The method according to claim 1 , wherein a priority between the communication devices is based on a type of the communication devices.
6 . The method according to claim 1 , wherein a communication device of the communication devices associated with an address having a lowest value has a highest priority among the communication devices.
7 . The method according to claim 1 , wherein a priority between the communication devices is inversely linked to a value of the addresses of the communication devices, ones of the addresses with lower values having higher priority than other ones of the addresses with higher values.
8 . The method according to claim 1 , wherein the addresses respectively associated with the communication devices are incremented by one bit.
9 . The method according to claim 1 , wherein after an expiration of a timer, the host device communicates with the communication devices that have not been polled before.
10 . A host device for polling communication devices in a communication system comprising the host device and the communication devices, wherein the host device is connected to the communication devices via a clock line for transmitting a clock signal to the communication devices and via an arbitration line implemented with “AND” logic for receiving arbitration signals transmitted by the communication devices, wherein each communication device is associated with an address, wherein each communication device is configured to pull up or down the arbitration line for sending an arbitration signal according to the associated address when the communication device is ready to send data to the host device, the host device comprising:
one or more network interfaces to communicate with the communication devices;
at least one memory configured to store processor-executable instructions; and
at least one processor configured to execute the processor-executable instructions to:
send a clock signal on the clock line during an arbitration cycle, causing the communication devices to send respective arbitration signals towards the arbitration line according to respective associated addresses from highest bit to lowest bit, during the arbitration cycle;
receive a final signal corresponding to a lowest address of the associated addresses, during the arbitration cycle, resulting from the “AND” logic applied to the arbitration signals;
select a communication device of the communication devices associated with the lowest address; and
poll the selected communication device to receive data from the selected communication device during a communication cycle.
11 . The host device according to claim 10 , wherein the address associated with a communication device is defined according to a priority between the communication devices.
12 . The host device according to claim 10 , wherein a priority between the communication devices is based on a type of the communication devices.
13 . The host device according to claim 10 , wherein the at least one processor is configured to execute the processor-executable instructions to determine that the communication device associated with an address having a lowest value has a highest priority among the communication devices.
14 . The host device according to claim 10 , wherein after an expiration of a timer, the at least one processor is configured to execute the processor-executable instructions to communicate with the communication devices that have not been polled before.
15 . A non-transitory computer readable storage medium comprising instructions that, when executed by at least one processor, causes the at least one processor to perform a method for polling communication devices in a communication system comprising a host device and the communication devices, wherein the host device is connected to the communication devices via a clock line for transmitting a clock signal to the communication devices and via an arbitration line implemented with “AND” logic for receiving arbitration signals transmitted by the communication devices, wherein each communication device is associated with an address, wherein each communication device is configured to pull up or down the arbitration line for sending an arbitration signal according to the associated address when the communication device is ready to send data to the host device, the method comprising:
sending a clock signal on the clock line during an arbitration cycle, causing the communication devices to send respective arbitration signals towards the arbitration line according to respective associated addresses from highest bit to lowest bit, during the arbitration cycle,
receiving a final signal corresponding to a lowest address of the associated addresses, during the arbitration cycle, resulting from the “AND” logic applied to the arbitration signals,
selecting a communication device of the communication devices associated with the lowest address, and
polling the selected communication device to receive data from the selected communication device during a communication cycle.
16 . The non-transitory computer readable storage medium according to claim 15 , wherein the address associated with a communication device is defined according to a priority between the communication devices.
17 . The non-transitory computer readable storage medium according to claim 15 , wherein a priority between the communication devices is based on a type of the communication devices.
18 . The non-transitory computer readable storage medium according to claim 15 , the method further comprising determining that the communication device associated with an address having a lowest value has a highest priority among the communication devices.
19 . The non-transitory computer readable storage medium according to claim 15 , wherein the addresses respectively associated with the communication devices are incremented by one bit.
20 . The non-transitory computer readable storage medium according to claim 15 , the method further comprising, after an expiration of a timer, causing the host device to communicate with the communication devices that have not been polled before.