M2i FIFO Mode

FIFO mode is used to record data continuously to or from the PC memory (RAM), or to the hard disk. (The direction depending on whether you are utilising a signal capture or signal generator card).

During data transfer the whole of on-board memory is used a FIFO buffer, this is interrupt driven and automatically controlled from the driver for best performance. It is a continuous operation and it is possible to empty part of the FIFO buffer whilst processing data in real time within your PC application. Data transfer is done by the driver in answer to a hardware interrupt and utilising a scatter-gather DMA technique, with transfer rates dependent on PC performance. The rates illustrated above for capture into PC RAM and are achievable by many PC's using the M2i series and C++ code. The conventional PCI bus will achieve about half this rate, but still fast enough for most applications. Keep in mind that hardware on the same bus share bandwidth, so using two or more boards can reduce the data transfer per board. Some mother boards have two or separate bus controllers which gets around this problem if boards are placed appropriately. Note that the recent development of another connection type known as PCI-Express (PCIe), does not suffer from this sharing limitation. Bus bandwidth aside FIFO streaming to RAM or hard disk drive has the great advantage of storage space, but keep in mind that a conventional IDE hard drive allows only about 20MBytes/sec transfer speed and thus provide a bottle neck to flow. Newer SATA drives can work at almost double this rate. Whatever method is used, recording of data starts with the trigger event and runs until the user stop command or user defined number sample segments have been collected.

FIFO mode may be combined with Multiple Recording / Replay as well as with Gated Sampling / Replay for greater capture control.