[Forgot the copy to the list.]
>>> Another question: According to the data sheet the output fifo has
>>> a depth of 4kBytes. In my experiments, it only buffers 1kB - is this
>>> a configuration issue, is the datasheet wrong, or am I missing
>>> something?
>>
>
> I'm not sure the ft2232h has a 4k output buffer. I remember vaguely
> that it has 4k buffer space. This is then shared between various
> functions, input, output, channel one, channel two.
Hm, the datasheet
http://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT2232H.pdf
on page 5, in the block diagram, shows 4 dual port buffers of 4kB each,
between the protocol engine and the MPSSE/Multipurpose UART/FIFO
controllers (one for RX, one for TX, for each channel).
On page 20:
> Dual Port FIFO TX Buffer (4Kbytes per interface). Data from the Host
PC is stored in these buffers
> to be used by the Multi-purpose UART/FIFO controllers. This is
controlled by the USB Protocol Engine and
> FIFO control block.
> Dual Port FIFO RX Buffer (4Kbytes per interface). Data from the
Multi-purpose UART/FIFO
> controllers is stored in these blocks to be sent back to the the Host
PC when requested. This is controlled
> by the USB Protocol Engine and FIFO control block.
So, I'm wondering: does the device need 4 bytes internally to transfer
1 byte to the output?
However, for me it's fine that it doesn't buffer so much data: it allows
me to interrupt the data flow more quickly.
Thomas
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