Rockwell Automation 20D PowerFlex 700S with Phase I Control Reference Manual - Manual (Page 51)

Rockwell Automation Publication PFLEX-RM002D-EN-E - August 2013 51
Detail Drive Configuration and Operation Chapter 1
Producer/Consumer Operation Overview
P/C messages operate at a higher priority than C/S messages and are used to
control/report the operation of the drive (for example start, stop, etc.). A P/C
status message is transmitted every 5 ms (by the drive) and a command message is
received from every change of state in any attached DPI peripheral. Change of
state is a button being pressed or error detected by a DPI peripheral. P/C
messages are of a fixed size, so support of message fragmentation is not required.
The following types of messaging are covered:
• Drive status (running, faulted, etc.)
• Drive commands (start, stop, etc.)
• Control logic parsing operations (for example, mask and owner
parameters)
• Entering Flash programming mode
• “Soft” login and logout of peripheral devices (enabling/disabling of
peripheral control)
Peer-to-Peer Operation
Peer-to-Peer messaging allows two devices to communicate directly rather than
through the master or host (i.e. drive). They are the same priority as C/S
messages and will occur in the background. If an LCD HIM is attached to the
PowerFlex 700S drive, it will be able to directly request off-board parameters
using Peer-to-Peer messages (i.e. no proxy support needed in the drive).
PowerFlex 700S drives can use all six communication ports because Peer-to-Peer
proxy operations are not needed. All Peer-to-Peer operations occur without any
intervention from the user (regardless whether proxy or normal P/P operation),
no setup is required. No Peer-to-Peer proxy operations are required while the
drive is in Flash mode.
All the timing requirements specified in the DPI system, Control, and Messaging
specifications are supported. Peripheral devices will be scanned (“pinged”) at a
10ms rate. Drive status messages will be produced at a 5 ms rate, while peripheral
command messages will be accepted (by the drive) as they occur (i.e. change of
state). Based on these timings, the following worst case conditions can occur
(independent of the baud rate and protocol):
• Change of peripheral state (for example, Start, Stop, etc.) to change in the
drive - 10 ms
• Change in reference value to change in drive operation - 10 ms
• Change in Datalink data value to change in the drive - 10 ms
• Change of parameter value into drive - 20ms times the number of attached
peripherals
The maximum time to detect the loss of communication from a peripheral device
is 500ms.