buffer size 6602?

[Tommi]

Hello,
I want to use the buffered measurement features of the 6602. But where can I find some information about the size of the buffer?

Regards Thomas

[Christian_L]

Thomas,

Most of the buffering is done in the memory on your system not on the card. The card has a 16 sample FIFO per DMA channel. When you configure a buffered operation, the board passed the data to the FIFO which is then send over DMA to the memory on your computer. The size of the buffer there is set by you in the application as part of configuring the operation and depends on how many samples you want to acquire. In a finite acquisition you should set the buffer size to the number of samples you want to acquire. In a continuous or double-buffered operation you select the buffer size according to how fast samples will be coming in and how often you want to read out the buffer.

You can run up to 3 counters in a buffered mode each with their own FIFO,
DMA channel, and buffer.

Christian L
NI Consulting Services

[StefanA]

The best way to get information about this is to look into the specifications.

I discovered last week that the 6602 has no buffer at all. The data will be send directly with DMA to the memory on your computer.

[John_P1]

Hi Stefan,

Technically the 6602 has a 2-sample on-board FIFO per channel to allow for simultaneous read/write to the buffer.  One consequence of this is lower transfer rates than some of our other devices.  In particular, the 621x family of M series boards has a 1024 sample FIFO per channel which allows for much higher transfer rates.  Other M Series have a similar 2 sample FIFO and cannot acquire from counters as quickly.

Data transfer rates on the counters is one feature where our new X Series boards really stand out from the others--they have been benchmarked up to 10 MHz per channel on all four counters.  I just wanted to make sure anyone who came across this thread knew of our other options that are now available.  I hope this helps!

-John