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petri_output(&net, p1, t1, 1); petri_output(&net, p3, t1, 1); petri_output(&net, p2, t2, 1); petri_output(&net, p4, t3, 1); petri_output(&net, p5, t3, 1); petri_output(&net, p6, t4, 1);

petri_add_tokens(&net, p1, 1); petri_add_tokens(&net, p2, 1); petri_add_tokens(&net, p5, 1); petri_add_tokens(&net, p6, 1);

petri_print(&net);

petri_event(&net, t1); petri_print(&net); petri_event(&net, t3); petri_print(&net); petri_event(&net, t4); petri_print(&net); petri_event(&net, t2); petri_print(&net); petri_event(&net, t4); petri_print(&net);

return error;

}

20.4.3 An Exclusive OR Transition:

The inhibitory inputs are complimentary to the exclusive or function. Thus another research proposed an Exclusive or transition which will fire when one (and only one) input is from a place with tokens. An example of a problem using this, a ring shift register was modelled. This net is modelled as shown below.

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In this example the EOR transition is marked with a plus in a circle (at ‘t7’). When run, a token will appear in p1, p3, and p5 in a repeating cycle. The program to set this up is seen below.

int test3() /*

*EOR TEST NET (Peterson book, 1981, discussed pg. 190)

*This is for a single bit shifter

*/

{

static int error;

static struct petri_net net;

static int p1, p2, p3, p4, p5, p6, p7, p8, p9, p10; static int t1, t2, t3, t4, t5, t6, t7;

error = petri_init(&net);

p1 = petri_place(&net, “p1”);

p2 = petri_place(&net, “p2”);

p3 = petri_place(&net, “p3”);

p4 = petri_place(&net, “p4”);

p5 = petri_place(&net, “p5”);

p6 = petri_place(&net, “p6”);

p7 = petri_place(&net, “p7”);

p8 = petri_place(&net, “p8”);

p9 = petri_place(&net, “p9”);

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p10 = petri_place(&net, “p10”);

t1 = petri_transition(&net, “t1”);

t2 = petri_transition(&net, “t2”);

t3 = petri_transition(&net, “t3”);

t4 = petri_transition(&net, “t4”);

t5 = petri_transition(&net, “t5”);

t6 = petri_transition(&net, “t6”);

t7 = petri_transition(&net, “t7”);

petri_input(&net, p6, t1, 1); petri_input(&net, p7, t1, 1); petri_input(&net, p2, t2, 1); petri_input(&net, p7, t2, 1); petri_input(&net, p4, t3, 1); petri_input(&net, p7, t3, 1); petri_input(&net, p1, t4, 1); petri_input(&net, p3, t5, 1); petri_input(&net, p5, t6, 1); petri_input(&net, p8, t7, 1); petri_input(&net, p9, t7, 1); petri_input(&net, p10, t7, 1);

petri_output(&net, p1, t1, 1); petri_output(&net, p3, t2, 1); petri_output(&net, p5, t3, 1); petri_output(&net, p2, t4, 1); petri_output(&net, p8, t4, 1); petri_output(&net, p4, t5, 1); petri_output(&net, p9, t5, 1); petri_output(&net, p6, t6, 1); petri_output(&net, p10, t6, 1); petri_output(&net, p7, t7, 1);

petri_type_transition(&net, t7, EOR);

petri_add_tokens(&net, p1, 1);

petri_print(&net);

petri_event(&net, t4); petri_print(&net); petri_event(&net, t7); petri_print(&net); petri_event(&net, t2); petri_print(&net); petri_event(&net, t5); petri_print(&net); petri_event(&net, t7); petri_print(&net); petri_event(&net, t3); petri_print(&net); petri_event(&net, t6); petri_print(&net); petri_event(&net, t7); petri_print(&net);

return error;

}