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50 MI.20xx Manual
Programming FIFO Mode
When using FIFO mode together with one of the options that allow to have gaps in the acquisiton like Multiple Recording or Gated Sampling
one can even run the board with higher sample rates. It just has to be sure that the average sample rate (calculated with acquisition time and
gap) does not exceed the above mentioned sample rate limitations.
The sample rate that can be run in one of these mode is depending on the number of channels that have been activated. Due to the internal
structure of the board this is limited to a internal throughput of 250 MB/s (250 MS/s):
Programming
The setup of FIFO mode is done with a few additional software registers described in this chapter. All the other settings can be used as des-
cribed before. In FIFO mode the register SPC_MEMSIZE and SPC_POSTTRIGGER are not used.
Software Buffers
This register defines the number of software buffers that should be used for FIFO mode. The number of hardware buffers is always two and
can not be changed by software.
When this manual was printed there are a total of 256 buffers possible. However if there are changes and enhancements to the driver in the
future it will be informative to read out the number of buffers the new driver version can hold.
The length of each buffer is defined in bytes. This length is used for hardware and software buffers as well. Both have the same length. The
maximum length that can be used is depending on the installed on-board memory.
Each FIFO buffer can be a maximum of half the memory. Be aware that the buffer length is given in overall bytes not in samples. Therefore
the value has to be calculated depending on the activated channels and the resolution of the board:
Theoretical maximum sample rate PCI Bus Throughput
1 Channel 100 MS/s [1 Channel] x [1 Byte per sample] * 100 MS/s = 100 MB/s
2 Channels 50 MS/s [2 Channels] x [1 Byte per sample] * 50 MS/s = 100 MB/s
4 Channels 25 MS/s [4 Channels] x [1 Byte per sample] * 25 MS/s = 100 MB/s
8 Channels 12.5 MS/s [8 Channels] x [1 Byte per sample] * 12.5 MS/s = 100 MB/s
Maximum sample rate that can be programmed Internal throughput
1 Channel 250 MS/s [1 Channel] x [1 Byte per sample] x 250 MS/s = 250 MB/s
2 Channels 125 MS/s [2 Channels] x [1 Byte per sample] x 125 MS/s = 250 MB/s
4 Channels 62.5 MS/s [4 Channels] x [1 Byte per sample] x 62.5 MS/s = 250 MB/s
8 Channels 31.25 MS/s [8 Channels] x [1 Byte per sample] x 31.25 MS/s = 250 MB/s
Register Value Direction Description
SPC_FIFO_BUFFERS 60000 r/w Number of software buffers to be used for FIFO mode. Value has to be between 2 and 256
Register Value Direction Description
SPC_FIFO_BUFADRCNT 60040 r Read out the number of available FIFO buffers
Register Value Direction Description
SPC_FIFO_BUFLEN 60010 r/w Length of each buffer in bytes. Must be a multiple of 1024 bytes.