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Subject: FT245R transfer rates

From: Jan Wilmans <janwilmans@xxxxxxxxx>
To: libftdi@xxxxxxxxxxxxxxxxxxxxxxx
Date: Mon, 22 Feb 2010 11:27:12 +0100

I'm using a FT245R in my design and I'm seeing fairly low transfer rates;
What I'm seeing on the FT245 side, is that RXF# is high most of the time, so it looks like
the host is not sending enough data / not fast enough or in too many short packets.

What I was wondering: the FT245R datasheet claims (quote:) "Data transfer rates up to 1Mbyte / second."

But, since it is a fullspeed device (1ms frames) and it has 128 byte receive buffer,
I figure the maximum tranfer rate is limited to 1000x 128 bytes per second? (equal 125Kb/s)

In other words: the receive buffer can be filled with at most 128 bytes every 1ms...

How is the 1 MB/s even theoretically possible with a 128 byte receive buffer?


Jan Wilmans

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