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Re: FIFO sizes



Hi Tom,

	For the system we are building we are using 256K word buffer for 16 MB/sec data rate.  Reason is that, we want to handle up to 15 ms for any unexpected delays in Master operation & any unexpected seek time on hard disk & to allow op sys to handle interrupt process current data setup for next transfer etc.  Since we need to run continously for several hours, with no data loss, we choose this size.

We tried with 4 kB fifo and see that, we fill it up quite often before we start reading.

>Hello All,
>
>I was wondering whether there are certain rules of thumb regarding the
>sizing of transmit/receive FIFO's for master operations.
>For our current application, we will need an average transfer rate of
>roughly 15 Mbytes/s, but this can arrive in bursts. What is the maximum
>time that we should buffer our data before we will get a grant from the
>PCI arbiter? (On a heavily loaded PC)
>Assuming that this time is 100 us, a buffer of 1500 bytes should be
>sufficient. Let's take 2k byte  to have some more margin. Is this a
>reasonble size that will avoid dropped data?
>
>Thank you,
>
>Tom Verbeure
>Design Engineer
>Alcatel Microelectronics
 

Ravi C. Kaipa     Ravi.Kaipa@GSFC.NASA.GOV
Code 553.2  PH: 301-286-7012, Fax: 301-286-1672 
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