Short Answers:
1) 64 "logical" channels and 2 "physical" channels (TC0 and TC1). 2) The QDMA channels are also logical. The actual transfers are handled by TC0 and TC1. Long Answer: There are two distinct pieces to the EDMA: the "channel controller" (CC) and the "transfer controller" (TC). The TC is what you are calling the "physical channel", i.e. it is physically connected to the Switched Central Resource and it is what actually does the reads and writes. I like to think of the TC as a "dumb" DMA. That is, it has no idea about all the events coming in from all the peripherals, all it knows about is how to read and write data. The CC on the other hand is the "brains" of the EDMA. The Event Register (ER) flags events coming in from the various peripherals. These 64 events can be thought of as logical channels. When the CC finds gets one of these events it will fetch the corresponding transfer information from the corresponding Parameter RAM set and submit and Transfer Request (TR) to the TC. The CC will actually use that Parameter Set as "scratch pad" where it will update things like the src and dst address, decrement the count, etc. That's why you need to have "reload" sets. Hopefully the above context will help you better understand the EDMA3 Reference Guide. Brad ________________________________ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Sandip Ray Sent: Thursday, March 06, 2008 6:36 AM To: davinci-linux-open-source@linux.davincidsp.com Subject: EDMA in DM6446 Hi, I have two queries regarding DMA in DM6446. 1. In DM6446, there are 64 EDMA channels. So whether these are logical or physical channels? What is the exact meaning of logical or physical channel? As per my understanding Logical channels means different logical events e.g Timer0 , Timer1 ..etc. & physical channels means seperate physical paths i.e different data buses. Please correct me if I am wrong on my understanding. 2. In DM6446, we have 8 QDMA channels. As qdma is not event triggered, whether these channels are physical channels? Thanks and Regards, Sandip
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