[Coco] Re: atari USB device
jdaggett at gate.net
jdaggett at gate.net
Mon Nov 22 16:42:34 EST 2004
Now that I can agree on.
james
On 22 Nov 2004 at 12:47, Dave Gacke wrote:
From: "Dave Gacke" <dgacke at ektarion.com>
To: "'CoCoList for Color Computer Enthusiasts'"
<coco at maltedmedia.com>
Subject: RE: [Coco] Re: atari USB device
Date sent: Mon, 22 Nov 2004 12:47:28 -0600
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> I guess what I'm getting at is this.
>
> At 1.5mbps (Low Speed USB) your poll intervals come at 10ms fixed.
>
> The packet sizes are 8 or up to 64 bytes, depending on which type of
> device it is.
>
> So it's either 800 bytes per second (8*100 polls/sec) or 6400 bytes
> per second. 8 byte report size is for interrupt device, 64 byte for
> isochronous or bulk.
>
> Both packet types will fit inside your allocated frame time.
>
>
>
>
> -----Original Message-----
> From: coco-bounces at maltedmedia.com
> [mailto:coco-bounces at maltedmedia.com] On Behalf Of jdaggett at gate.net
> Sent: Monday, November 22, 2004 10:20 AM To: CoCoList for Color
> Computer Enthusiasts Subject: RE: [Coco] Re: atari USB device
>
> Dave
>
> Where I was definitely wrong on the Isochronous mode is that the limit
> is 1023 bytes per pipe, not packet.
>
> My understanding is at 1.5 Mbps, one bit time is 667 nS. So in 1 mS
> one can transmit 1500 bits or ~187 bytes theoretically. Add in the
> overhead for polling and the actual data bytes transmitted is markably
> reduced. It seems realistic that 8 bytes to 64 bytes of actual data
> would be a limiting amount in what can be sent in the 1 mS time slot.
>
> Considering that there initially be few devices on the bus,
> peripherals like the keyboard or mouse can be allocated more
> bandwidth.
>
> james
>
>
> On 22 Nov 2004 at 8:51, Dave Gacke wrote:
>
> From: "Dave Gacke" <dgacke at ektarion.com>
> To: "'CoCoList for Color Computer Enthusiasts'"
> <coco at maltedmedia.com>
> Subject: RE: [Coco] Re: atari USB device
> Date sent: Mon, 22 Nov 2004 08:51:29 -0600
> Send reply to: CoCoList for Color Computer Enthusiasts
> <coco at maltedmedia.com>
> <mailto:coco-
> request at maltedmedia.com?subject=unsubscribe>
> <mailto:coco-
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>
> > Hi James,
> >
> > Unfortunately your math is a little off.
> >
> > The part that everyone seems to miss about USB is the poll time.
> > Since it is a polled device bus, at low speed, your polls come at
> > 10ms intervals, and full speed they are at 1ms, and I forget what
> > they are at high speed.
> >
> > Anyway, you are severely limited by the rate at which you are
> > polled. Per poll you can pass 1 packet, so its easy to figure out
> > the throughput from that.
> >
> >
> > Dave
> >
> > -----Original Message-----
> > From: coco-bounces at maltedmedia.com
> > [mailto:coco-bounces at maltedmedia.com] On Behalf Of jdaggett at gate.net
> > Sent: Sunday, November 21, 2004 7:34 PM To:
> > msmcdoug at optushome.com.au; CoCoList for Color Computer Enthusiasts
> > Subject: Re: [Coco] Re: atari USB device
> >
> > Mark
> >
> > In handshake mode at high speed the data payload is either 8, 16,
> > 32, or 64 bytes. In Low speed mode the max data payload is 8 bytes.
> > Well capable for the Coco.
> >
> > Isochronous mode, without hondshakes, the data payload is limited
> > to 1023 bytes.
> >
> > This is per the copy of the USB 1.1 Specs that I have.
> >
> > I personally think that Isochronous mode should never need to be
> > used.
> >
> >
> > What Torsten was thinking of was that a sector size for a Coco disk
> > is 256 bytes. The SL811HS has the upper sixteen bytes of the buffer
> > reserved for registers. This would leave the largest packet data
> > size of 240 bytes. That ends up being 16 bytes shy of a disk sector.
> >
> >
> > The only way to read a complete sector would be to break the
> > sector up into 4 64 byte packets. Each packet would take 42.7
> > microseconds to transfer and about 512 machine cycles to do a
> > load and store for the Coco. At high speed that is about 286.2
> > micro seconds. Essential about 1.5 milliseconds to transfer data
> > from a disk into the Coco.
> >
> > Not sure if we gain that much speed advantage. But maybe some. The
> > Disk drive itself is really the slow element of the whole process.
> >
> >
> > james
> >
> >
> > On 22 Nov 2004 at 9:42, Mark McDougall wrote:
> >
> > Date sent: Mon, 22 Nov 2004 09:42:27 +1100
> > From: Mark McDougall
> > <msmcdoug at optushome.com.au>
> > Organization: Technetium Development Pty Ltd
> > To: CoCoList for Color Computer Enthusiasts
> > <coco at maltedmedia.com>
> > Subject: Re: [Coco] Re: atari USB device
> > Send reply to: msmcdoug at optushome.com.au,
> > CoCoList for Color Computer Enthusiasts
> > <coco at maltedmedia.com>
> > <mailto:coco-
> > request at maltedmedia.com?subject=unsubscribe>
> > <mailto:coco-
> > request at maltedmedia.com?subject=subscribe>
> >
> > > USB data packets (at least v1.x) are only 64 bytes in length. So
> > > I'm not sure what the 240 bytes refers to in your post. With the
> > > USB protocol handling the handshaking the CoCo is left to emptying
> > > the 64-byte packets as fast (or as slow) as it likes. I really
> > > don't see an issue here.
> >
> >
> >
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