Why ACK should be deasserted sometimes during the data acquisition with PCI-DIO-32HS burst mode handshaking?

[EK]

My peripheral device sends 32-bit data to the DIO board serially with PCLK 6MHz, about 300,000 times totally. The phenomenan like I mentioned in the summary above happens, and it causes some data missings.
Though I know ACK is not always asserted as somewhere in the NI database says, I want to know why it happens. if I can. I wonder if it is just inevitable or not.
Do I only have to add some buffer memories to my device and make it watch on the ACK changing? Or, is there any other good way to avoid this problem?

[Michael_S.]

Hi,

Burst mode handshaking protocol needs to conditions to be meet before data can be transfered. The PCI-DIO-32HS need to be ready to transfer data and the external device needs to be ready to transfer data.
The ACK line tells the external device when the PCI-DIO-32HS is ready and the REQ line tells the PCI-DIO-32HS when the external device is ready. When both are ready data should be transfered. This is the nature of Handshaking, guarenteed data transfer (when both devices are ready), but not at a guarenteed rate. Handshaking means that the two devices communicate with each other to determine when to transfer data.

The PCI-DIO-32HS ACK line is toggling low because the PCI-DIO-32HS is busy catching up with the given transfer and is not ready to receive m
ore data at this time. The ACK line is not something you can control, it is controlled by the PCI-DIO-32HS.

Your application may be better suited for use with Pattern I/O if you are not using the handshaking lines, ACK and REQ, to control the flow of data. Pattern I/O does not use handshaking lines and clocks data in on every rising edge of the clock. You may receive an error if your system can not keep up with the transfer rate.