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SynqNet Timing Values

During SynqNet initialization, the network timing schedule is calculated based on the discovered nodes and data packet sizes. The SynqNet timing values provide detailed information about the update periods, latencies, calculation times, packet spacing, upstream/downstream payload times, and network bandwidth usage. These values allow you to evaluate the network performance. The SynqNet Timing Values are available from the MPI and are defined below.

The following values are from MPISynqNetTiming.

controllerFreq

The sample rate calculation of the SynqNet controller board, in kHz. It is also the rate at which SynqNet packets are sent. The controllerFreq must be configured so that the driveUpdateFreq is an integer multiple of the controllerFreq.

This value is configurable. See MPIControlConfig.

controllerPeriod

The sample period calculation of the SynqNet controller board, in uS. Derived from controllerFreq.

txTime

The scheduled time for SynqNet packets to be sent, in % (of the controllerPeriod). Defaults to 75%. Must be set to a value greater than the foreground calculation time, and less than 100%.

This value is configurable. See MPIControlConfig.

calculationLimit

The maximum allowed foreground calculation time, in µs. Derived from txTime * controllerPeriod.

driveUpdateFreq

The cyclic communication rate of a drive processor on a SynqNet node, in kHz. Typically fixed to 16 kHz, but may vary depending on drive type. May be configurable on some drives. This rate often matches the drive PWM rate.

driveUpdatePeriod

The cyclic communication period of a drive processor on a SynqNet node, in uS. Derived from driveUpdateFreq.

bandwidthUsage

The amount of SynqNet bandwidth used, in %, for this SynqNet configuration. The actual packet payload configured is divided by the maximum available SynqNet bandwidth, for both upstream and downstream packets. The greater of the two is reported.

calculationTime

The foreground calculation time of the controller, in µs.

calculationSlack

The available slack time between the foreground calculation time, and the scheduled txTime, in uS.

demandLatency

The time to send SynqNet demand data downstream from controller to nodes, in µs. Does not include drive demand delays.

feedbackLatency

The time to send SynqNet feedback data upstream from nodes to controller, in uS. Rounded up to make the total SynqNet latency an integer multiple of the driveUpdatePeriod. Does not include drive feedback delays.

latencySlack

The slack time from the configured feedbackLatency (which is rounded up to an integer multiple of the driveUpdatePeriod), to the minimum possible upstream delay, in µs.

controlLatency

The overall SynqNet system control latency, in µs. Always rounded up to an integer multiple of driveUpdatePeriod. Control latency begins when position feedback is sampled on the node, includes upstream packet delays, controller foreground calculation, downstream packet delays, and ends when demands are strobed on the nodes. Note drive feedback and demand delays are NOT included. Control latency can be broken down into the four components listed below: feedbackLatency, calculationTime, calculationSlack, and demandLatency.

synq

Downstream SYNQ packet payload, in µs. Includes spacing between packets.

demand

Downstream DEMAND packet payload, in µs. Includes spacing between packets.

control

Downstream CONTROL packet payload, in µs. Includes spacing between packets.

downstream

Total downstream (controller to nodes) packet payload, in uS. Includes spacing between packets. Breaks down into the following three packet types.

feedback

Upstream FEEDBACK packet payload, in µs. Includes spacing between packets.

status

Upstream STATUS packet payload, in µs. Includes spacing between packets.

upstream

Total upstream (nodes to controller) packet payload, in µs. Includes spacing between packets. Breaks down into the following two packet types.

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