CompuScope SDK Manua.. - Egmont Instruments

ticks = GetTickCount();while (gage_busy ()){if (GetTickCount() > ticks + BUSY_TIMEOUT) {gage_abort_capture (board.source);return (0);}}Transferring the CompuScope DataThe acquired CompuScope data can be transferred when the board is no longer busy, and the gage_busyroutine returns a 0. First, the location of the sampled data within on-board CompuScope memory isdetermined with a call to the gage_calculate_addresses routine. This routine returns the start address, thetrigger address and the end address that are required to determine the location of data that was capturedinto CompuScope memory.CompuScope memory is organized as a circular buffer, so that direct numerical comparisons of theaddresses should be avoided. For instance, because the memory counter rolls over when the acquisitionreaches the end of on-board memory, the end address may actually have a lower numerical value than thestart address. Naively subtracting the start address from the end address in order to determine thecapture length would therefore incorrectly yield a negative number. The gage_normalize_address routine,which accounts for memory roll-over, can be used for such comparisons.Before data transfer, the CompuScope must be prepared for data transfer using the gage_need_ramroutine. Generally, the application should call gage_need_ram(1) before transferring data and shouldcall gage_need_ram(0) after data transfer is complete.The recommended method of retrieving data from CompuScope on-board acquisition memory is thegage_transfer_buffer_3 routine. This routine transfers data using PCI bus-mastering of large data blocks,if supported by the CompuScope hardware. PCI bus-mastering is the fastest method of transferring dataacross the PCI bus. It requires no CPU arbitration and bus-mastering transfer rates can be sustained at upto 100 Mega Bytes per second. Gage_transfer_buffer_3 also automatically interleaves data from bothADC memory bank when operating CompuScope hardware in single channel mode.Other CompuScope data transfer methods are described in the CompuScope API Reference Manual forolder Gage users. These routines are not recommended, however, for new designs.Page 36CompuScope SDK Manual