Справочник Пользователя для IBM MiEM78P468N
EM78P468N/EM78P468L
8-Bit Microcontroller
30
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Product Specification (V1.5) 02.15.2007
(This specification is subject to change without further notice)
6.6 Oscillator
6.6.1 Oscillator
Modes
The EM78P468N/EM78P468L can operate in three different oscillator modes i.e.,
a.) Main oscillator (R-OSCI, OSCO), such as RC oscillator with external resistor and
Internal capacitor mode (ERIC); b.) Crystal oscillator mode; and c.) PLL operation
mode (R-OSCI connected to 0.01
μF capacitor to Ground). User can select which
mode by programming FMMD1 and FMMD0 in the Code Options Register. The
sub-oscillator can be operated in Crystal mode and ERIC mode. Table 3 below shows
how these three modes are defined.
Table 3 Oscillator Modes as defined by FSMD, FMMD1, FMMD0.
FSMD
FMMD1
FMMD0
Main Clock
Sub-clock
0
0
0
RC type (ERIC)
RC type (ERIC)
0
0
1
Crystal type
RC type (ERIC)
0 1
×
PLL type
RC type (ERIC)
1
0
0
RC type (ERIC)
Crystal type
1
0
1
Crystal type
Crystal type
1 1
×
PLL type
Crystal type
Table 4 Summary of maximum operating speeds
Conditions
VDD
Fxt Max. (MHz)
2.3 4
3.0 8
Two clocks
5.0 10
6.6.2
Phase Lock Loop (PLL Mode)
When operate on PLL mode, the High frequency determined by sub-oscillator. We can
choose RD register to change high oscillator frequency. The relation between high
frequency (Fm) and sub-oscillator is shown as below table:
Xout
Xin
XTAL
0.01uF
C2
C1
R-OSCI
EM78P468N
Fig. 6-6 PLL Mode Circuit