Chapter 4 ProgrammingPCI E Series RLPM4-58 ©National Instruments CorporationMake sure that the same logical channel is not assigned to more thanone resource.DMA requests are generated when all of the above mentionedinitializations are done and when the source is programmed appropriately.For analog input, the AIFREQ signal from the DAQ-STC is used as theDMA source. For more information, see Chapter 2 of the DAQ-STCTechnical Reference Manual. By using the FIFO_Request_Selectionfunction, you can generate DMA requests based on any of thefollowing conditions:• FIFO not empty• FIFO half-full• FIFO full• FIFO half-full until FIFO is emptyFor analog output, the AOFREQ signal from the DAQ-STC is used as theDMA source. By using the AO_FIFO function you can generate DMArequests based on any of the following conditions:• FIFO empty• FIFO less than half-full• FIFO not full• Assert on FIFO half-full and deassert on FIFO fullFor general-purpose counter/timers, an interrupt is produced in bufferedmodes, such as the buffered event counting, the buffered periodmeasurement, and so on. The secondary bank of interrupts in the DAQ-STCis used for generating DMA requests for the general-purposecounter/timers.The Link Chaining Mode for DMA TransferThe MITE contains DMA channels that may be used to transfer data to theI/O and CPU port. Each channel supports several modes of operation. Oneof the modes of operation is the Link Chaining Mode. It enables the user todo DMA transfers, limited only by the size of the memory space. This modeof operation is used in analog input Example 4. The Link Chaining Moderequires a linked list structure to store the information for each buffer. Thelinked list structure enables DMA transfers on different memory segmentsand makes seamless data transfer possible.Inside the linked list structure, each node contains values for TCR, MAR,DAR, and LKAR. TCR (Transfer Count Register) stores the total number
