# DMA Channel Not Started when changing data rates

**URL:** <https://discuss.pynq.io/t/dma-channel-not-started-when-changing-data-rates/1410>\
**Category:** Support\
**Created:** [June 25, 2020, 3:10am UTC](https://discuss.pynq.io/t/dma-channel-not-started-when-changing-data-rates/1410 "2020-06-25T03:10:54Z")\
**Posts on this page:** 1\
**Showing post:** 11

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**Author:** ![cathalmccabe](https://sea1.discourse-cdn.com/flex019/user_avatar/discuss.pynq.io/cathalmccabe/32/3348_2.png) [@cathalmccabe](https://discuss.pynq.io/u/cathalmccabe)\
**Post date:** [July 21, 2020, 6:30am UTC](https://discuss.pynq.io/t/dma-channel-not-started-when-changing-data-rates/1410/11 "2020-07-21T06:30:35Z")

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TLAST signals the end of a transfer. If you hold it high, it ends after the first data beat no matter what the transfer length was.  
If you have an AXI stream input and output, you could pass through TLAST (from input to output) adding any required delays. Otherwise you would need to calculate when you need TLAST to be high and generate this yourself.

Cathal

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