CompuScope SDK Manua.. - Egmont Instruments

gage_transfer_buffer_3
Syntax
C:
uInt32 GAGEAPI gage_transfer_buffer_3 (int32 ta, int16 channel, void far *buffer, int32 nsamples);
Visual BASIC:
Function gage_transfer_buffer_3 (ByVal ta As Long, ByVal channel As Integer, buffer As Integer, ByVal
nsamples As Integer) As Integer
Remarks
gage_transfer_buffer_3 is used to copy nsamples points from the specified channel to the supplied
buffer beginning from address ta. The channel can be either GAGE_CHAN_A or GAGE_CHAN_B. The
relevant addresses can be obtained by calling gage_calculate_addresses. . The buffer must have been
previously typecast to the appropriate size. For 8 bit CompuScopes, the buffer should typecast for uInt8
values. For CompuScopes with more than 8 bit resolution, the buffer should typecast for int16 values.
The CompuScope PCI boards will use PCI bus-mastering if available in hardware, otherwise a CPU
mediated PCI data transfer method is used. PCI bus-mastering is the fastest possible PCI data transfer
method.
The buffer must be padded so that it is slightly longer than the memory required to store nsample samples.
The required amount of padding is different for different CompuScope models. The best padding method
is to use the variable user_buffer_padding, which is returned by the drivers and is the amount of extra
padding in Bytes required for the current CompuScope model.. Simply add user_buffer_padding to the
amount of memory to be allocated.
Unlike gage_transfer_buffer, in single channel mode gage_transfer_buffer_3 automatically downloads
data from both CompuScope A/D converter memories and internally interleaves them. Consequently,
the user application does not need to interleave the data when the acquisition has been performed in
single channel mode using gage_transfer_buffer_3. In single channel mode, gage_transfer_buffer_3
need only be called once with channel equal to GAGE_CHAN_A
Return Value
Returns an offset from the beginning of the dword-aligned buffer that the driver uses.
Internally using PCI bus-mastering, PCI CompuScope hardware can only transfer data from a d-word (4
byte) boundary in CompuScope on-board memory. For instance, data can be downloaded starting from
hexadecimal addresses 0x3000 or 3004, but not starting from hexadecimal addresses 0x3001.
The returned offset gives the byte address location of the address ta, specified in the call to
gage_transfer_buffer_3. For instance, if ta were equal to hex 0x3003, then the CompuScope would be
forced to download data from hexadecimal addresses 0x3000. The offset would then be returned as
0x3003 – 0x3000 = 3.
See also: gage_transfer_buffer and Appendix: Comparison of Various Data Transfer Routines.
Examples:
CompuScope API Reference Manual
53