39.4.1 External Clock/Oscillator Timing Requirements

Figure 39-4. Clock Timing
Note: See table below.
Table 39-7. 
Standard Operating Conditions (unless otherwise stated)
Param No. Sym. Characteristic Min. Typ. † Max. Units Conditions
ECL External Clock
OS1 FECL Clock Frequency — — 1 MHz
OS2 TECL_DC Clock Duty Cycle 40 — 60 %
ECM External Clock
OS3 FECM Clock Frequency — — 16 MHz
OS4 TECM_DC Clock Duty Cycle 40 — 60 %
ECH External Clock
OS5 FECH Clock Frequency — — 64 MHz
OS6 TECH_DC Clock Duty Cycle 40 — 60 %
LP Oscillator
OS7 FLP Clock Frequency — — 100 kHz Note 4
XT Oscillator
OS8 FXT Clock Frequency — — 4 MHz Note 4
HS Oscillator
OS9 FHS Clock Frequency — — 20 MHz VDD>2.5V Note 4
Secondary Oscillator
OS10 FSEC Clock Frequency 32.4 32.768 33.1 kHz Note 4
System Oscillator
OS20 FOSC System Clock Frequency — — 64 MHz (Note 2, Note 3)
OS21 FCY Instruction Frequency — FOSC/4 — MHz
OS22 TCY Instruction Period 62.5 1/FCY — ns
Note:
  1. Instruction cycle period (TCY) equals four times the input oscillator time base period. All specified values are based on characterization data for that particular oscillator type under standard operating conditions with the device executing code. Exceeding these specified limits may result in an unstable oscillator operation and/or higher than expected current consumption. All devices are tested to operate at “min” values with an external clock applied to OSC1 pin. When an external clock input is used, the “max” cycle time limit is “DC” (no clock) for all devices.
  2. The system clock frequency (FOSC) is selected by the “main clock switch controls” as described in the “Power-Saving Operation Modes” section.
  3. The system clock frequency (FOSC) must meet the voltage requirements defined in the "Standard Operating Conditions" section.
  4. LP, XT and HS oscillator modes require an appropriate crystal or resonator to be connected to the device. For clocking the device with the external square wave, one of the EC mode selections must be used.