Re: Question about PIC16F84A internal oscillator and instructions
Same as several other ancient PIC16 devices,
PIC16F84A have External RC oscillator mode for the CPU oscillator.
External in this context mean that you provide R and C connected to the oscillator input pin, Pin 16 OSC1/CLKIN.
It is shown in page 23, section 6.2.3 RC Oscillator, in the datasheet.
It is selected by the default value of FOSC bits in configuration word.