CCS C Compiler Manual PCB / PCM / PCH

}
byte changes;
changes = last_b ^ port_b;
last_b = port_b;
if (bit_test(changes,4 )&& !bit_test(last_b,4)){
//b4 went low
}
if (bit_test(changes,5)&& !bit_test (last_b,5)){
//b5 went low
}
.
.
.
delay_ms (100); //debounce
The delay=ms (100) is a quick and dirty debounce. In general, you will not want to sit in an ISR
for 100 MS to allow the switch to debounce. A more elegant solution is to set a timer on the first
interrupt and wait until the timer overflows. Do not process further changes on the pin.
How do I directly read/write to internal registers?
A hardware register may be mapped to a C variable to allow direct read and write capability to
the register. The following is an example using the TIMER0 register:
#BYTE timer 0 = 0x 01
timer0= 128; //set timer0 to 128
while (timer 0 ! = 200); // wait for timer0 to reach 200
Bits in registers may also be mapped as follows:
#BIT T 0 IF = 0x 0B.2
.
.
.
while (!T 0 IF); //wait for timer0 interrupt
Registers may be indirectly addressed as shown in the following example:
printf ("enter address:");
a = gethex ();
printf ("\r\n value is %x\r\n", *a);
The compiler has a large set of built-in functions that will allow one to perform the most common
tasks with C function calls. When possible, it is best to use the built-in functions rather than
directly write to registers. Register locations change between chips and some register
operations require a specific algorithm to be performed when a register value is changed. The
compiler also takes into account known chip errata in the implementation of the built-in
functions. For example, it is better to do set_tris_ A (0); rather than *0x 85 =0;
How do I do a printf to a string?
The following is an example of how to direct the output of a printf to a string. We used the \f to
indicate the start of the string.
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