Datasheet

I/O Signals
MC68HC908GR16 Data Sheet, Rev. 5.0
Freescale Semiconductor 67
Figure 4-2. CGM External Connections
4.4 I/O Signals
The following paragraphs describe the CGM I/O signals.
4.4.1 Crystal Amplifier Input Pin (OSC1)
The OSC1 pin is an input to the crystal oscillator amplifier.
4.4.2 Crystal Amplifier Output Pin (OSC2)
The OSC2 pin is the output of the crystal oscillator inverting amplifier.
4.4.3 External Filter Capacitor Pin (CGMXFC)
The CGMXFC pin is required by the loop filter to filter out phase corrections. An external filter network is
connected to this pin. (See Figure 4-2.)
NOTE
To prevent noise problems, the filter network should be placed as close to
the CGMXFC pin as possible, with minimum routing distances and no
routing of other signals across the network.
OSC1
C1 C2
SIMOSCEN
CGMXCLK
R
B
X1
R
S
C
BYP
OSC2
CGMXFC
V
DDA
Note: Filter network in box can be replaced with a single capacitor, but will degrade stability.
V
DD
OSCSTOPENB
(FROM CONFIG)
R
F1
C
F2
C
F1
V
SSA