Spectrum Brands MI.20xx Manuel D’Utilisation
Standard acquisition modes
General Information
(c) Spectrum GmbH
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Standard acquisition modes
General Information
The standard mode is the easiest and mostly used mode to acquire analog data with a Spectrum A/D board. In standard recording mode
the board is working totally independant from the host system (in most cases a standard PC), after the board setup is done. The advantage
of the Spectrum boards is that regardless to the system usage the board will sample with equidistant time intervals.
The sampled and converted data is stored in the onboard memory and is held there for being read out after the acquisition. This mode allows
sampling at very high conversion rates without the need to transfer the data into the memory of the host system at high speed.
After the recording is done, the data can be read out by the user and is transfered via the PCI bus into PC memory.
the board is working totally independant from the host system (in most cases a standard PC), after the board setup is done. The advantage
of the Spectrum boards is that regardless to the system usage the board will sample with equidistant time intervals.
The sampled and converted data is stored in the onboard memory and is held there for being read out after the acquisition. This mode allows
sampling at very high conversion rates without the need to transfer the data into the memory of the host system at high speed.
After the recording is done, the data can be read out by the user and is transfered via the PCI bus into PC memory.
This standard recording mode is the most common mode for all ana-
log acquisition and oscilloscope boards. The data is written to a
programmed amount of the onboard memory (memsize). That part
of memory is used as a ringbuffer, and recording is done conti-
nuously until a triggerevent is detected. After the trigger event, a
certain programmable amount of data is recorded (posttrigger) and
then the recording finishes. Due to the continuously ringbuffer recor-
ding, there are also samples prior to the triggerevent in the memory
(pretrigger).
log acquisition and oscilloscope boards. The data is written to a
programmed amount of the onboard memory (memsize). That part
of memory is used as a ringbuffer, and recording is done conti-
nuously until a triggerevent is detected. After the trigger event, a
certain programmable amount of data is recorded (posttrigger) and
then the recording finishes. Due to the continuously ringbuffer recor-
ding, there are also samples prior to the triggerevent in the memory
(pretrigger).
When the board is started the pretrigger is filled up with data first. While doing this the board’s trigger de-
tection is not armed. If you use a huge pretrigger size and a slow sample rate it can take up some time after
starting the board before a trigger event will be detected.
tection is not armed. If you use a huge pretrigger size and a slow sample rate it can take up some time after
starting the board before a trigger event will be detected.
Programming
Memory, Pre- and Posttrigger
At first you have to define, how many samples are to be recorded at all and how many of them should be acquired after the triggerevent has
been detected.
been detected.
You can access these settings by the registers SPC_MEMSIZE, which sets the total amount of data that is recorded, and the register
SPC_POSTTRIGGER, that defines the number of samples to be recorded after the triggerevent has been detected. The size of the pretrigger
results on the simple formula:
SPC_POSTTRIGGER, that defines the number of samples to be recorded after the triggerevent has been detected. The size of the pretrigger
results on the simple formula:
pretrigger = memsize - posttrigger
The maximum memsize that can be use for recording is of course limited by the installed amount of memory and by the number of channels
to be recorded. The following table gives you an overview on the maximum memsize in relation to the installed memory.
to be recorded. The following table gives you an overview on the maximum memsize in relation to the installed memory.
Maximum memsize
How to read this table: If you have installed the standard amount of 16 MSample on your 2021 board and you want to record all four
channels, you have a total maximum memory of 16 MSample * 1/4 = 4 MSample per channel for your data.
channels, you have a total maximum memory of 16 MSample * 1/4 = 4 MSample per channel for your data.
The maximum settings for the post counter are limited by the hardware, because the post counter has a limited range for counting. The settings
depend on the number of activated channels, as the table below is showing.
depend on the number of activated channels, as the table below is showing.
Maximum posttrigger in MSamples
The amount of memory that can be either set for the used memsize and postcounter values can only be set by certain steps. These steps are
results of the internal memory organization. For this reason these steps also define the minimum size for the data memory and the postcounter.
results of the internal memory organization. For this reason these steps also define the minimum size for the data memory and the postcounter.
Register
Value
Direction
Description
SPC_MEMSIZE
10000
r/w
Sets the memory size in samples per channel.
SPC_POSTTRIGGER
10100
r/w
Sets the number of samples to be recorded after the trigger event has been detected.
20
20
20
21
20
30
20
31
ch0
ch1
ch2
ch3
x
1/1
1/1
1/1
1/1
x
x
1/2.
1/2
1/2
1/2
x
x
n.a.
1/2
n.a.
1/2
x
x
x
x
n.a.
1/4
n.a.
1/4
20
20
20
21
20
30
20
31
ch0
ch1
ch2
ch3
x
256
256
256
256
x
x
128
128
128
128
x
x
n.a.
256
n.a.
256
x
x
x
x
n.a.
128
n.a.
128