Download 8XC196MC, 8XC196MD, 8XC196MH Microcontroller User`s Manual

8XC196MC, MD, MH USER’S MANUAL
XTAL1
TXTAL1
TXTAL1
1 State Time
1 State Time
PH1
PH2
CLKOUT
Phase 1
Phase 2
Phase 1
Phase 2
A0114-04
Figure 2-4. Internal Clock Phases
The combined period of phase 1 and phase 2 of the internal CLKOUT signal defines the basic
time unit known as a state time or state. Table 2-2 lists state time durations at various frequencies.
Table 2-2. State Times at Various Frequencies
FXTAL1
(Frequency Input to the
Divide-by-two Circuit)
State Time
8 MHz
250 ns
12 MHz
167 ns
16 MHz
125 ns
The following formulas calculate the frequency of PH1 and PH2, the duration of a state time, and
the duration of a clock period (TXTAL1).
F XT AL1
PH1 (in MHz) = ------------------- = PH2
2
2
State Time (in µs) = ------------------FXTAL1
1
T XTAL1 = ------------------F XTAL1
Because the microcontroller can operate at many frequencies, this manual defines time requirements (such as instruction execution times) in terms of state times rather than specific measurements. Datasheets list AC characteristics in terms of clock periods (T XTAL1 or TOSC).
2.5
INTERNAL PERIPHERALS
The internal peripheral modules provide special functions for a variety of applications. This section provides a brief description of the peripherals; subsequent chapters describe them in detail.
2-8