Once Parapin has been initialized (Section 5), and pins have been configured as output pins (Section 6), values can be asserted on those pins using the following functions:
void set_pin(int pins);
void clear_pin(int pins);
void change_pin(int pins, int state);
The pins argument of all three functions accepts the LP_PINnn constants described in Section 3. set_pin turns pins on, electrically asserting high TTL values. clear_pin turns pins off, electrically asserting low TTL values. The convenience function change_pin does the same thing as set_pin and clear_pin; its state argument takes one of the constants LP_SET or LP_CLEAR. Calling change_pin(pins, LP_SET) has exactly the same effect as calling set_pin(pins).
These three functions will only have effects on pins that were previously configured as output pins as described in Section 6. Attempting to assert a value on an input pin will have no effect.
Note that while the direction of Pins 2-9 must be the same at all times (i.e., either all input or all output), the actual values of these pins are individually controllable when they are in output mode.
Examples:
pin_output_mode(LP_PIN01|LP_DATA_PINS|LP_PIN14|LP_PIN16|LP_PIN17);
/* All these pins are now in output mode */
set_pin(LP_PIN01 | LP_PIN04 | LP_PIN07 | LP_PIN14 | LP_PIN16);
/* Pins 1, 4, 7, 14, and 16 are all on */
clear_pin(LP_PIN01 | LP_PIN16);
/* Pins 1 and 16 are now off */
change_pin(LP_PIN01 | LP_PIN02, some_integer ? LP_SET : LP_CLEAR);
/* Pins 1 and 2 are now off if and only if some_integer == 0 */