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.
| 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.
|
