CCS C Compiler Manual PCB / PCM / PCH

Common Questions & Answers
If nothing is seen coming back (except the initial "Start"), check the RCV pin on the PIC®
with a logic probe. You should see a HIGH state and when a key is pressed at the PC, a
pulse to low. Trace back to find out where it is lost.
5. The PIC® is always receiving data via RS-232 even when none is being sent.
A. Check that the INVERT option in the USE RS232 is right for your level converter. If
the RCV pin is HIGH when no data is being sent, you should NOT use INVERT. If the pin
is low when no data is being sent, you need to use INVERT.
B. Check that the pin is stable at HIGH or LOW in accordance with A above when no
data is being sent.
C. When using PORT A with a device that supports the SETUP_ADC_PORTS function
make sure the port is set to digital inputs. This is not the default. The same is true for
devices with a comparator on PORT A.
6. Compiler reports INVALID BAUD RATE.
A. When using a software RS232 (no built-in UART), the clock cannot be really slow
when fast baud rates are used and cannot be really fast with slow baud
rates. Experiment with the clock/baud rate values to find your limits.
B. When using the built-in UART, the requested baud rate must be within 3% of a rate
that can be achieved for no error to occur. Some parts have internal bugs with BRGH set
to 1 and the compiler will not use this unless you specify BRGH1OK in the #USE RS232
directive.
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