STISIM Drive (SDL) - DO - Digital Output

This event allows you to send digital outputs to external equipment during simulation runs. The AO, CAO, DO, and TDO events are the only way you can control external equipment during a simulation run. This event works slightly different in STISIM Drive than it did in the DOS version of STISIM. The simulation allows you to specify the output of up to 12 individual pins on the I/O card. These outputs are processed through port B (pins 3-10, 8 bits) and through the high portion of port C (pins 22-25, 4 bits). Review the hardware section for information on the output boards support and how to configure them. In addition, if you will be using the DO event you must make sure that the digital I/O option has been enabled in STISIM Drive's configuration. To enable the digital I/O, simply check the box on the I/O controls tab found in the configuration option.

EVENT PARAMETERS:

PARAMETER 1:

Number that sets the specified pin’s outputs to high (1) or low (0). In the DOS version of STISIM this operation was done with 2 parameters, but now it only requires this single parameter. The I/O card is automatically configured so that there are 12 bits that you can set to either high (1) or low (0). The first 4 bits of the number are the high portion of Port C while the final 8 bits are from Port B.          Port C High:  Port B: Bits:  {12 11 10 9}  {8 7 6 5 4 3 2 1} When you decide which pins you will change, simply use the Windows scientific calculator in binary mode to specify the bits, then convert it into a decimal number and use this number as the input. Because STISIM Drive is used for a variety of applications, sometimes we add a custom option that will not be useful for everyone but is available for everyone to use. The DO event is one of these options. Several researchers that use STISIM Drive need real-time information about potential time to collisions (TTCs). In order for them to receive this data in real-time, STISIM Drive sends a digital signal that is proportional to the TTC. In order to use this special option you must set this parameter to a negative value. If this parameter is set to a negative value (we use –1) then at each simulation frame time, STISIM Drive will send out the smallest value of TTC that it computes (TTC is computed for each non cross traffic, CT, vehicle in the display scene). There are a couple of limits to this approach: 1. Since the TTC is sent continuously during the run, you can not use the DI and TDO events at all, and you can only use the DO event for sending TTC. 2. The data that is sent is 12 bits and needs to be divided by 1000 in order to compute the actual TTC value.

EXAMPLES:

100,DO,32
1000,DO,256

This event was designed to give the user some control over external hardware without having to change the STISIM Drive software. For example, you can control an external computer by sending bits of information from STISIM Drive to the computer and then having the external computer interpret this data and then act on it. The first example simply sets bit 6 of Port B (pin 5 on the CIO-DIO-24 board) to high, and clears all remaining pins (pin 5 set high the rest set low). If the second example was used in the same scenario as the first, then at 1000 feet pin 5 would go low (because bit 6 is being set to 0) while pin 25 would be set high because bit 9 (in the number 256) is set to high.