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National Instruments 778980-01 Serial Interface Device 

National Instruments part number 778980-01 is an identifying part number for the PCI-8431/2, a Serial Interface with 2 Ports and a maximum baud rate of 3000 kbits/s. This interface provides superior communication speed between devices. It supports large DMA transfers, multiple threads, and a wide range of processors. Users can choose between 2 to 4 line handset modes. Serial lines appear as standard COM ports, ensuring compatibility with programs that use serial communications. The interface offers two standard data transfer methods: direct memory access (DMA) and interrupt request (IRQ), which facilitate data transfer from serial hardware to the computer’s memory. 

The 778980-01 Serial Interface utilizes the NI-MITE ASIC with PCI bus mastering to perform DMA transfers independently of the CPU. This capability allows the Serial Interface to transfer data from the FIFO to memory even when the CPU is busy handling other requests. The device features 2 ports with a DB-9 male connector, supports a maximum baud rate of 3 Mbps, and has a FIFO size of 128 bytes. It requires a power supply of +5 VDC at 500 mA, with a peak demand of up to 700 mA. 

Users can employ two standard data transfer methods: direct memory access (DMA) and interrupt request (IRQ). DMA allows data transfer from serial hardware to PC memory without involving the CPU, enabling efficient data handling. IRQ, on the other hand, signals the processor each time data is ready to be processed, interrupting its current tasks to handle the data transfer. When a user has 100 bytes of data at a serial port, the processor transfers this data to memory. 

As the data volume increases, so does the processing power needed for the transfer. DMA (Direct Memory Access) facilitates data transfer directly from the serial board to PC memory, bypassing the processor entirely. The 778980-01 Serial Interface leverages DMA technology for data transfers. Users can enhance DMA transfer speeds by utilizing the NI-MITE ASIC, scatter-gather technology, and bus mastering.