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USS library and PKW Words

Created by: bakerjw at: 8/10/2009 9:20 PM (5 Replies)

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8/10/2009 9:20 PM	Rate (0)
bakerjw Posts: 126 Rating: (18)	When using the USS library on the S7-1200 the PKW words on the motor drive must be set to 4. If the motor drive is set to 127 (variable length) then the motor drive will accept commands but no response will be acknowledged by the USS_DRV function block. On most drives the PKW word length parameter is P2013.
bakerjw Posts: 126 Rating: (18)
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8/17/2009 3:49 PM	Rate (0)
Robster Gold Expert Joined: 5/28/2008 Last visit: 3/1/2023 Posts: 1343 Rating: (139)	Thanks for this information. Maybe this link helps in first steps of USS communication with S7-1200 http://support.automation.siemens.com/WW/view/en/37604154

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8/20/2009 12:35 PM	Rate (0)
Denilson Pegaia Platinum Expert Joined: 9/23/2005 Last visit: 3/13/2023 Posts: 4180 Rating: (1331)	Hi, Thanks for your tip. I note also, that with 127 the speed actual value comes always 0.
	Denilson Pegaia Siemens Industry Sector Technical Support
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8/20/2009 1:07 PM	Rate (0)
Robster Gold Expert Joined: 5/28/2008 Last visit: 3/1/2023 Posts: 1343 Rating: (139)	Pegaia Hi, Thanks for your tip. I note also, that with 127 the speed actual value comes always 0. It's because you get no response from drive.

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8/24/2009 2:13 PM	Rate (0)
bakerjw Posts: 126 Rating: (18)	Actually you do receive a response from the drive when it is set to 127. The drive will see 4 PKW words as a valid datagram and will respond in one of 2 ways. Some drives when set to variable length PKW words (127) will respond with the same number of PKW words as were received (4 PKW words in means 4 PKW words out). With those you should get a speed response since the speed is returned in PZD word #2 (status is in PZD word #1) and has no connection to PKW words. For drives that do not respond with 4 PKW words, the USS_PORT FB will return an error code of 0x818B with the USS drive number in the hidden Extended_Error output of USS_PORT. We're running some tests with drives containing older firmware to get an idea of how they respond to 4 PKW words when set to variable length (127).
bakerjw Posts: 126 Rating: (18)
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10/15/2014 9:15 AM	Rate (0)
Min_Moderator Platinum Member Joined: 9/3/2014 Last visit: 3/13/2019 Posts: 4827 Rating: (123)	New question published bysoulstone is split to a separate thread with the subject when comumnicating Micromaster 420 to Motor, Motor not RUN. Best regards Min_Moderator

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