LEGO MINDSTORMS Robots Manual page 58

These commands set the mode and direction of the outputs in one fell swoop, but you should still set the power level explicitly with a call to SetPower().
For timed actions, the following command will come in handy:
OnFor(const outputs, expression time)
This command turns on the specified outputs for the given time, measured in hundredths of a second. Then the given outputs are turned off (in brake mode, not in float mode).
The following example runs outputs A and C forward, waits one second, then reverses outputs A and C. After another second, the outputs are turned off.
task main() {
SetPower(OUT_A + OUT_C, OUT_HALF);
Fwd(OUT_A + OUT_C);
OnFor(OUT_A + OUT_C, 100);
Rev(OUT_A + OUT_C);
OnFor(OUT_A + OUT_C, 100);
}
The On(), Off(), Float(), Fwd(), Rev(), and Toggle() commands are really shorthand for these lower-level output commands:
SetOutput(const outputs, const mode)
This command sets the mode for the given outputs. The outputs are specified in the same way as in the Fwd() and Rev() commands. The value of mode should be one of the constants
OUT_ON, OUT_OFF, and OUT_FLOAT.
SetDirection(const outputs, const direction)
This command determines the direction of the supplied outputs. The direction parameter should be OUT_FWD, OUT_REV, or OUT_TOGGLE. OUT_TOGGLE is a special value that sets the
direction of the output to the opposite of its current value.
In general, I recommend you don't call SetDirection() with the OUT_TOGGLE value. If you explicitly set the directions of your outputs, your program will be clearer. Furthermore, in
programs with more than one task, your program is more likely to behave as you expect.
Input Commands
Before you can read a value from one of the RCX's inputs, you need to tell the RCX what type of sensor is attached to the input. NQC provides a command that does just this:
SetSensor(expression sensor, const configuration)
This command tells the RCX how to configure the given input. Valid values for sensor are SENSOR_1, SENSOR_2, and SENSOR_3, which represent the three inputs of the RCX. The sensor
configurations are detailed in Table 4-1. See Appendix A, Finding Parts and Programming Environments, which lists the sensors that are available for the RCX.
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