Allen-Bradley devicenet modules in logix5000 control systems Manual Do Utilizador
Publication DNET-UM004A-EN-P - March 2004
11-2 Tune the Performance of a DeviceNet Network
Factors that Effect
Performance
Performance
The following example shows how different I/O or network
parameters effect the performance of the network.
parameters effect the performance of the network.
Interscan delay
• Scanner continues to get polled data from slower responders or
larger devices.
• Communication with software such as RSLinx and RSNetWorx
occurs (upload, download, browse, etc.)
Px – Scanner sends data to a polled device.
Prx – Polled device sends input data to scanner.
Prx – Polled device sends input data to scanner.
x is the address of a device.
Polled update
3 data at address 3 changes
scanner gets the data
P1
Pr1
P2
Pr2
P3 Pr3 P4 Pr4 P5 Pr5
P1
Pr1
P2
Pr2
P3 Pr3 P4 Pr4 P5 Pr5
Scan Cycle
S – Scanner sends strobe request.
Srx – Strobed devices send input data to scanner.
Srx – Strobed devices send input data to scanner.
x is the address of a device.
Change of state (COS)
3 data at address 3 changes
scanner gets the data
P1
Pr1
P2
Pr2
P4 Pr4 P5 C3 Pr5
P1
Pr1
P2
Pr2
P4 Pr4 P5 Pr5
S
Sr3 Sr4 Sr5 P1
Pr1
P2
Pr2
S
Sr3 Sr4 Sr5 P1
Pr1
P2
Pr2
Strobed update
3 data at address 3 changes
scanner gets the data
P1
Pr1
P3 Pr3 P4 Pr4 P5 Pr5
P2
Pr2
P3 Pr3 P4 Pr4 P5 Pr5
Background poll
3 data at address 3 changes
scanner gets the data
Shorter interscan delay
3 data at address 3 changes
scanner gets the data
P1
Pr1
P2
Pr2
P3 Pr3 P4 Pr4 P5 Pr5
P1
Pr1
P2
Pr2
P3 Pr3 P4 Pr4 P5 Pr5