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8-1
CHAPTER 8
SPECIAL OPERATING MODES
8.1 CLOCK CIRCUITRY
The 87C196CB’s idle, powerdown, and ONCE modes are the same as those of the 8XC196NT.
The only difference is in the way that the power saving modes disable the clock circuitry (Figure
8-1).
Figure 8-1. Clock Circuitry
A3168-01
Clock
Generators
CPU Clocks (PH1, PH2)
Divide-by-two
Circuit
PLLEN
Phase-locked Loop
Clock Multiplier
Phase
Comparator
Filter
Phase-
locked
Oscillator
Disable
PLL
(Powerdown)
Peripheral Clocks (PH1, PH2)
CLKOUT
Disable Clocks
(Powerdown)
Disable Clocks
(Idle, Powerdown)
XTAL1
XTAL2
F
XTAL1
Disable
Oscillator
(Powerdown)
Disable Clock Input
(Powerdown)
f
F
XTAL1
4F
XTAL1
f
2