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If the A/D converter will be used, connect V
during A/D conversions. Even if the A/D converter will not be used, V
connected to provide power to port 0. On the 8XC196MC and MD, they also provide power to
port 1. Refer to "Analog Ground and Reference Voltages" on page 12-12 for a detailed discussion
of A/D power and ground recommendations.
Multilayer printed circuit boards with separate V
noise. For more information on noise protection, refer to AP-125, Designing Microcontroller Sys-
tems for Noisy Environments and AP-711, EMI Design Techniques for Microcontrollers in Auto-
motive Applications.
13.4 THE ON-CHIP OSCILLATOR CIRCUITRY
The on-chip oscillator circuit (Figure 13-3) consists of a crystal-controlled, positive reactance os-
cillator. In this application, the crystal operates in a parallel resonance mode. The feedback resis-
tor, Rf, consists of paralleled n-channel and p-channel FETs controlled by the internal powerdown
signal. In powerdown mode, Rf acts as an open and the output drivers are disabled, which disables
the oscillator. Both the XTAL1 and XTAL2 pins have built-in electrostatic discharge (ESD) pro-
tection.
to a separate reference supply to minimize noise
REF
To internal
circuitry
Rf
XTAL1
(Input)
Oscillator Enable#
(from powerdown circuitry)
Figure 13-3. On-chip Oscillator Circuit
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MINIMUM HARDWARE CONSIDERATIONS
REF
and ground planes also help to minimize
CC
V CC
XTAL2
(Output)
V SS
and ANGND must be
A0076-03
13-5
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