CompuScope SDK Manua.. - Egmont Instruments

the data whose address was specified by the trigger_view_offset global driver variable. For
instance, let us assume that the user requested transfer of data starting from CompuScope onboard
memory address hex 0x3002. This is done by passing 0x3002 as the first argument to
gage_transfer_buffer_3 or by setting the value of the trigger_view_offset global driver variable to
0x3002 before calling gage_trigger_view_transfer_3 Due to its hardware architecture, the
CompuScope would be forced to download data from hexadecimal addresses 0x3000.
gage_transfer_buffer_3 and gage_trigger_view_transfer_3 would then return an offset with the
value of 0x3002 – 0x3000 = 2. This returned offset of 2 indicates that the start of the requested
data is in the 3 rd byte of the host memory buffer (0 means 1 st Byte, 1 means 2nd Byte, etc).
2. The second feature is that the data from both A/D converter memories are automatically
interleaved in single channel mode. Behind the scenes in single channel mode, both
gage_transfer_buffer_3 and gage_trigger_view_transfer_3 download the data from both A/D
converter memories and interleaves them within the driver. The user is then presented with the
complete single channel mode data record. Therefore, the application does not need to interleave
the data when the acquisition has been performed in single channel mode. By contrast, in the
case of gage_transfer_buffer, gage_trigger_view_transfer, gage_transfer_buffer_2 and
gage_trigger_view_transfer_2, it is the application’s responsibility to interleave the transferred
data in single channel mode. Since they are easier to use, therefore, gage_transfer_buffer_3 or
gage_trigger_view_transfer_3 should be used for new software development.
Single Sample Access Routines
gage_mem_read_chan_a and gage_mem_read_chan_b
These functions read one sample (which is 1 byte for 8 bit CompuScope boards and 2 bytes for 12, 14 and
16 bit CompuScope boards) from CompuScope on-board memory for channel A or channel B respectively
in dual channel mode. The functions are usually used to read relatively small amounts of data or to read
non-sequential data from a CompuScope board regardless of the operating mode.
gage_mem_read_dual is very similar to gage_mem_read_chan_a and gage_mem_read_chan_b. It
reads one sample from CompuScope memory in dual channel mode, having the channel number as one of
the parameters. This function is best suited for an application where there is prior knowledge that the data
acquisition will be occurring in dual channel mode and both channels should be read.
gage_mem_read_single is the counterpart of gage_mem_read_chan_a and gage_mem_read_chan_b for
single channel mode. All three of these routines maintain the same parameters and return values
gage_mem_read_master reads one sample from CompuScope memory for channel A of the Master
CompuScope board. The Gage drivers detect the mode of operation, single or dual channel. This function
is mostly used in conjunction with gage_calculate_mra_addresses to read embedded enhanced trigger bits
from CompuScope memory. Embedded ETB information must always be read from the Master
CompuScope.
All Single Sample Access or gage_mem_read routines provide a “read ahead” caching mechanism, which
reads a larger block of data from the CompuScope memory behind the scenes. This allows faster response
of multiple calls to a gage_mem_read routine in order to download sequential data points. The size of the
cache buffer, however, varies among the CompuScope boards. When call to a gage_mem_read routine is
made, behind the scenes the driver downloads a multi-point block of data from CompuScope memory.
This block is then stored in the driver and is used as long as address locations for subsequent
gage_mem_read calls fall within it.
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