6.1 General Limitations

Limitations that apply to all devices are listed below. Some devices may have specific limitations.

Note: If you have trouble with I/O pins on processors that have A/D (e.g., PIC16F877A), make certain that the ADCON registers are configuring those pins for digital I/O rather than for analog input. For most processors, these default to analog inputs and the associated pins cannot be used for I/O until the ADCON (or ADCON1) register is set properly.
  • MPLAB X Simulator is a discrete-event (as opposed to real-time) simulator.
  • Interrupt latency may not be accurate.
  • The internal oscillator can be changed in software, but will not effect of the speed of the oscillator during runtime.
  • Register Injection cannot be applied to GPRs declared using either EQU directive or CBLOCK directive in absolute mode.
  • Invalid pin names appear in midrange devices with alternate pin functions

    Some 8-bit devices implement alternate pin functionality. The pin diagram will show the same signal (e.g. “P2A”) on two different physical pins, and a register, typically APFCON, is used to specify which physical pin the signal is currently mapped to. The simulator needs a way to distinguish between the two instances of the signal, so it renames the signals by adding the associated APFCON field value to the signal name, (e.g. “P2A0”, “P2A1”). A side effect is that the renamed signals will appear in the pin list in the simulator's pin dialog. These modified signal names can be safely ignored.

  • For devices with the listed peripherals, the following limitations apply:
    • Timer1 increments on RC0, not RC1, for Timer1 enabled.
    • PWM output resolution is limited to 1 Tcy.