topic edma on dspi is so ineffective in ColdFire/68K Microcontrollers and Processors

edma on dspi is so ineffective

yan211 — Fri, 25 Nov 2011 20:52:17 GMT

I am working on the powerfull mcf54415,In my eyes ,the edma can get all out of the chip,but when i dive into the spi code, i was comfused. the edma did nothing ,but make thing conplicate.it just transfer 16 byte a time, then in the enoq interrupt ,it trigger rx edma channel to get the rx byte to dma buffer, then copy to user buffer,SO what the use of edma.

Can any one give a explain? Can i make the dma to transfer 1MB a time with just a interrupt?

Re: edma on dspi is so ineffective

JimDon — Sat, 26 Nov 2011 13:05:22 GMT

That was what I thought as well. If you have to copy it to the registers, whats the point?

Re: edma on dspi is so ineffective

yan211 — Tue, 29 Nov 2011 09:59:34 GMT

thank the reply, when I try the spi, set the pcs to sck delay to 5us,then i got byte to byte delay 5us,how could get fast byte transfer and remain pcs to sck delay. can someone help me out?

Re: edma on dspi is so ineffective

yan211 — Tue, 29 Nov 2011 10:24:55 GMT

too fast to ask! now i try to use different CTAR, got the expect!!so versatile the dspi