Rockwell Automation 20D PowerFlex 700S AC Drives with Phase II Control Reference Manual User Manual

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Rockwell Automation Publication PFLEX-RM003E-EN-E - January 2011

Chapter 1 Detailed Drive Operation

All the timing requirements specified in the DPI system, Control, and Messaging
specifications are supported. Peripheral devices will be scanned (“pinged”) at a 10
ms 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 (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 - 20 ms times the number of attached

peripherals

The maximum time to detect the loss of communication from a peripheral device
is 500 ms.

The following timing specifications apply to DPI devices:

• Host status messages only go out to peripherals once they log in and at least

every 125 ms (to all attached peripherals). Peripherals will time-out if more
than 250 ms passes without a response. Actual time is dependent on the
number of peripherals attached. The minimum time goal is 5 ms (may have
to be dependent on the Port Baud Rate). DPI allows a minimum 5 ms
status at 125 KB and 1ms status at 500 KB.

• The host determines the Minimum Update Time (MUT) based on the

number of attached peripherals. Range of values from 2…125 ms.
Minimum goal time of 5 ms. DPI allows 2 ms at 500 KB and 5 ms
minimum at 125 KB.

• Peripheral command messages (including Datalinks) generated on change-

of-state, but not faster than Host MUT and at least every 250 ms. Host
will time out if it is more then 500 ms.

• Peer messages requests cannot be sent any faster than 2x of MUT.

• Host must ping every port at least every 2 seconds. Peripherals time if more

then 3 seconds pass. Host will wait a maximum of 10 ms (125 KB) or 5 ms
(500 KB) for peripheral response to ping. Peripherals typical response time
is 1 ms. Periphals allow only one pending explicit message (i.e. ping
response or peer request) at a time.

• Response to an explicit request or fragment must occur within 1 second or

device will time out (applies to Host or Peripheral). Time-out implies retry
from beginning. Maximum number of fragments per transaction is 16.
Flash memory is exception with 22 fragments allowed.