Measurement Computing Personal488 rev.3.0 - Manual (Page 53)

Personal488 for Windows 95/98/Me/NT/2000 04-09-01 Hardware Configuration Reference 4-13
The GP488B/MM interface board may be set to interrupt the PC on the occurrence of certain hardware
conditions. The level of the interrupt generated is set by JP3. The GP488B/MM adheres to the “AT-style”
interrupt sharing conventions. When an interrupt occurs, the interrupting device must be reset by writing to
I/O address
02FX , where X is the interrupt level (from 0 to 7). This interrupt response level is set by
switches 1, 2, and 3 of SW1 which must be set to correspond to the JP3 interrupt level setting.
Configuring the GP488B/MM PC104 Interface DMA Channel
JP 2
C h an ne l 1
G P 4 8 8B /M M P C 1 0 4 D M A C ha n n el S e le ctio n s
C h an ne l 2 C h an ne l 3
The factory default DMA channel is 1. If this creates a conflict, reset jumper JP2 according to the figure.
If reset, record the new DMA channel being used.
Direct Memory Access (DMA) is a high-speed method of transferring data from or to a peripheral, such as
a digitizing oscilloscope, to or from the PC’s memory. The PC has four DMA channels, but Channel 0
(Disabled) is used for memory refresh and is not available for peripheral data transfer. Channel 2 is usually
used by the floppy disk controller, and is also unavailable. Channel 3 is often used by the hard disk
controller in PCs, XTs, and the PS/2 with the ISA bus, but is usually not used in ATs. So, depending on
your hardware, DMA Channels 1 and possibly Channel 3 are available. Under some rare conditions, it is
possible for high-speed transfers on DMA Channel 1 to demand so much of the available bus bandwidth
that simultaneous access of a floppy controller will be starved for data due to the relative priorities of the
two channels.