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Message
From: meizhangxiong <meizx@i...>
Date: Wed, 24 Jul 2002 16:40:46 +0800
Subject: [usb] dma
hi,all
I have there questions about Mr. Rudolf Usselmann's usb device core.
1,In the document,USB Function IP Core 3.1.1,the usb core surports a double buffering feature,and data is being retrieved/filled from/to the buffers in a round robin fation. In this document 3.2,however,in DMA mode,only one buffer(buffer 0)is used,buffer 1 is never used in DMA mode.I want to know if there is any conflition between these two representations and why.
2,In the interupt servcie routine,how do the buffer0/buffer1 exchange data with usb funtion controller?By DMA mode?
3,In usbf_pe.v,the following sentence,
// New Size (to be written to register file)
always @(posedge clk)
new_sizeb <= #1 (out_op & dma_en) ? max_pl_sz : (in_op ? size_next : sizu_c);
Does it mean that usb core use max_pl_sz space for each output transaction?
Regards
meizhangxiong
meizx@i...
2002-07-24
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