em78p468l ELAN Microelectronics Corp, em78p468l Datasheet - Page 36

• Manufacturer Part Number: em78p468l
• Description: 8-bit Microcontroller
• Manufacturer: ELAN Microelectronics Corp

EM78P468N/EM78P468L
8-Bit Microcontroller
30 •
6.6 Oscillator
6.6.1 Oscillator Modes
6.6.2
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 μ F 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.
Table 4 Summary of maximum operating speeds
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:
FSMD
0
0
0
1
1
1
Phase Lock Loop (PLL Mode)
Conditions
Two clocks
FMMD1
0
0
1
0
0
1
EM78P468N
FMMD0
0
1
×
0
1
×
R-OSCI
Xout
Xin
Fig. 6-6 PLL Mode Circuit
RC type (ERIC)
Crystal type
PLL type
RC type (ERIC)
Crystal type
PLL type
VDD
2.3
3.0
5.0
(This specification is subject to change without further notice)
XTAL
Main Clock
Product Specification (V1.5) 02.15.2007
Fxt Max. (MHz)
0.01uF
C1
C2
10
4
8
RC type (ERIC)
RC type (ERIC)
RC type (ERIC)
Crystal type
Crystal type
Crystal type
Sub-clock