GMS81C7216 Datasheet, PDF (84/121 Pages) List of Unclassifed Manufacturers – 8-BIT SINGLE-CHIP MICROCONTROLLERS

GMS81C7208/7216
21. OSCILLATOR CIRCUIT
The GMS81C7208/16 has two oscillation circuits internally. X_IN
and X_OUT are input and output for main frequency and SX_IN and
SX_OUT are input and output for sub frequency, respectively, in-
verting amplifier which can be configured for being used as an
on-chip oscillator, as shown in Figure 21-1. To use RC oscillation
instead of crystal, user should check mark on the “MASK OR-
DER & VERIFICATION SHEET” of the appendix of this man-
ual. However in the OTP device, when the programming RC
oscillation can be selected or not into the configuration bit. For
more detail, refer to "24.1 OTP Programming" on page 84.
Note: When using the sub clock oscillation, connect a re-
sistor in series with R which is shown as below figure.
In order to reduce the power consumption, the sub clock
oscillator employs a low amplification factor circuit. Be-
cause of this, the sub clock oscillator is more sensitive to
noise than the main system clock oscillator.
C1
X_OUT
C2
4.19MHz
X_IN
V_SS
Recommend
Crystal Oscillator
Ceramic Resonator
C1,C2 = 20pF
C1,C2 = 30pF
Crystal or ceramic oscillator
Open
External Clock
X_OUT
X_IN
R_EXT
X_OUT
For selection R value,
X_IN
Refer to AC Characteristics
External Oscillator
RC Oscillator (mask option)
Figure 21-1 Oscillation Circuit
Oscillation circuit is designed to be used either with a ceramic
resonator or crystal oscillator. Since each crystal and ceramic res-
onator have their own characteristics, the user should consult the
crystal manufacturer for appropriate values of external compo-
nents.
Oscillation circuit is designed to be used either with a ceramic
resonator or crystal oscillator. Since each crystal and ceramic res-
X_OUT
onator have their own characteristics, the user should consult the
crystal manufacturer for appropriate values of external compo-
X_IN
nents. In addition, see Figure 21-2 for the layout of the crystal.
Note: Minimize the wiring length. Do not allow the wiring to
intersect with other signal conductors. Do not allow the wir-
ing to come near changing high current. Set the potential of
the grounding position of the oscillator capacitor to that of
VSS. Do not ground it to any ground pattern where high cur-
rent is present. Do not fetch signals from the oscillator.
Figure 21-2 Recommend Layout of Oscillator PCB
Circuit
80
FEB. 2005 Ver 1.04