12.4.3.2 Primary Oscillator Pin Functionality

The POSC pins (OSCI and OSCO) can be used for other functions when the oscillator is not being used. The POSCMD[1:0] bits in the Oscillator Configuration register (OSCCFG) determine the oscillator pin function. The POSCIOFNC bit (OSCCFG) determines the OSCO pin function.

POSCIOFNC: OSCO Pin Function bit (except in XT and HS modes):

  • 1 = OSCO is the clock output and the instruction cycle (FCY) clock is output on the OCSO pin (see Figure 12-12)
  • 0 = OSCO is a general purpose digital I/O pin

The oscillator pin functions are provided in Table 12-34.

Table 12-34. Clock Pin Function Selection
Oscillator SourcePOSCIOFNC ValuePOSCMD[1:0] ValueOSCI

Pin Function(1)

OSCO

Pin Function(2)

POSC 
Disabled111Digital I/OClock Output
POSC 
Disabled011Digital I/ODigital I/O
HSx10OSCIOSCO
MSx01OSCIOSCO
EC100OSCIClock Output
EC000—Digital I/O
Note:
  1. OSCI pin function is determined by the Primary Oscillator Mode Selection (POSCMOD[1:0]) 
Configuration bits.
  2. OSCO pin function is determined by the Primary Oscillator Mode Selection (POSCMOD[1:0]), OSCIOFNC Configuration bits.
Figure 12-12. OSCO Pin for Clock Output (in EC Mode)