Chapter 7 Digital I/ODAQ-STC Technical Reference Manual7-12 ©National Instruments Corporationserial digital output line during the time required for eight bits to be output serially, you canalso omit the Serial DIO Wait Loop section from your program.To perform several serial digital I/O operations in sequence, the Serial DIO Wait Loop isnecessary; however, you can exclude the Serial DIO Setup section from the programmingsequence for all 8-bit data entities except the first.Note To perform serial output without the serial input, the value inDIO_Serial_Data_In_St will become undefined. You can perform serial output onpin DIO0 and ignore serial input data. You cannot perform hardware-controlledserial input on pin DIO4 and software-controlled parallel output on pin DIO0 atthe same time unless you want to keep the same value on the pin DIO0 for theduration of the serial DIO. In this case you should program eight instances of thisvalue in the DIO_Serial_Data_Out field before the serial DIO operation begins.7.6.2.3 Software-Controlled Serial Digital I/OIf hardware-controlled serial digital I/O is not used, the EXTSTROBE/SDCLK pin can beused as a digital output line. This enables you to select the direction of the eight DIO<0..7>pins and the EXTSTROBE/SDCLK pin for creating simple digital communication protocols.For example, you can configure pin DIO0 for output and pin DIO4 for input and performoperations similar to the one described in section 7.6.2.2, Hardware-Controlled Serial DigitalI/O. To use the EXTSTROBE/SDCLK pin it this way, you must disable hardware control ofit by setting the following bitfield.DIO_HW_Serial_Enable = 0;Use the following function to control the value on the EXTSTROBE/SDCLK pin:Function DIO_Clock_Out{DIO_Software_Serial_Control = 0 (for logic low) or 1 (for logic high);}7.6.2.4 Programming the Control LinesUse the following function to set the generic control lines:Function MSC_Generic_Control{Control = output value;}Note These are generic control lines. Refer to the user manual for your DAQ board ordevice for information on how these lines are used.
