Tom, If the ~10.5Mbit/s is continuous USB bandwidth required, a) The Bus is going to be struggling - remember that only 90% bandwidth is available for Iso and Int transfers, and with USB overheads, theoretical max transfer rate is 1.28MB/s (10.2Mbit/s) (USB spec 1.1, pg 42). Int and Bulk xfers are slightly worst due to extra USB overheads. b) The Intel device would be struggling - it only clocks at 12MHz and although I believe it now only requires 1 clock per state, at 1.28MB/s, you have to fully process 1 byte every 800ns. even just picking it up into the Acc would take 170ns AFAIK. If the buffer ever became full, you'll have to get the bytes out within the remains of that particular frame, which would be about 80 ns per byte. c) You have to guarentee that the whole USB is available Some people have other devices on the USB. Upto 126 other devices :-) d) From my personal experience, getting 5Mbit/s from the USB is all I'd try for in a real world situation. And that's with a parallel interface, DMA and/or probably with a 100MHz Scenix on the device end. This is written only as a reality check - We need people using USB to get it into the homebrew domain more. More USB stuff at:- http://ourworld.compuserve.com/homepages/steve_lawther/usbdev.htm Steve Lawther PS - apologies for the length of the disclaimer my employer feels is necessary. > -----Original Message----- > From: Thomas Brandon [SMTP:tom@PSY.UNSW.EDU.AU] > Sent: Monday, July 19, 1999 2:21 AM > To: PICLIST@MITVMA.MIT.EDU > Subject: Re: USB PICs (or Digital Audio via USB & MCU) > - At least 1 if not 2 channels of DAT quality I/O (24 bit, 48kHz, > stereo > x 4 = 1152 Kbyte/s. 2 isochronous capable endpoint pairs) > - 2 MIDI I/O (4x ~30000bps max. = 15Kbytes/s. 1 endpoint pair.) > - 1 channel of MPEG/AC-3 compressed audio (<200bit/s = <25Kbytes/s, 1 > isochronous endpoint (output only).) > - Full control over both audio and MIDI interfaces (at least 1 control > endpoint (BTW: anyone know if I can do the control for both MIDI and Dig. > Audio on 1 endpoint?)) > > Total: 1300Kbytes/s (not including protocol overhead) = ~10.5Mbit/s > One product I am looking at carefully is the Intel > USB MCUs. These are basically a MCS251 with an inbuilt USB interface. They > provide a few advantages over the Phillips that I can see: > - Speed. They support the full 12Mbit/s standard apparently. > - Buffering. They have 1 Mbyte of RAM available for buffering. Thus it > can be configured to give 256, 512 or 1024 bytes of buffer for 2 of the > ports which should be plenty (the other 2 have 16byte which should be fine > for MIDI/control. > ------------------- DISCLAIMER This email and any attachments are confidential and intended solely for the use of the individual or entity to whom they are addressed. Any views or opinions expressed are solely those of the author and do not necessarily represent those of WPI Husky Technology. If you are not the intended recipient, be advised that you have received this email in error and that any use, dissemination, forwarding, printing, or copying of this mail is strictly prohibited.