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USB Low-Full-High Speed Peripherals

Anonymous
Not applicable

Hi everybody!

   

Page 21 of AN56377 (Revision *J) mentions that PSoC supports a maximum packet size of 64 bytes using the Store-and-Forward mode and a maximum packet size of 1023 bytes using Cut-through mode. Table 18 in the same docuument (page 20-21) shows that Store-and-Forward mode is applicable to 'No DMA transfer / Manual DMA mode' and Cut-through mode is applicable only for Automatic DMA mode.

   

Does this mean that if we use Manual DMA mode for ISOC transfer from both Host to PSoC 5LP and from PSoC 5LP to Host, we need to configure the USBFS for Maximum packet size of 64 bytes? If we need to configure USBFS for Maximum packet size of 512 bytes, then should we only use the automatic DMA mode?

   

Thanks.

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Anonymous
Not applicable

 Hi,

   

The total sum of max packet size of all end points should not be greater than 512 unless memory management is set to "DMA with automatic MM".

   

It is because USB block has 512 bytes of RAM. But when DMA is used you do not have this limitation as DMA makes use of device RAM which is up to 8kB. 

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