em78p468n ELAN Microelectronics Corp, em78p468n Datasheet - Page 36

• Manufacturer Part Number: em78p468n
• Description: 8-bit Microcontroller
• Manufacturer: ELAN Microelectronics Corp

EM78P468N/L
8-Bit Microcontroller
30 •
6.6 Oscillator
6.6.1 Oscillator Modes
The EM78P468N/EM78P468L can operate in three different oscillator modes:
a.) Main oscillator (R-OSCI, OSCO), such as RC oscillator with external resistor and
b.) Crystal oscillator mode
c.) PLL operation mode (R-OSCI connected to 0.01μF capacitor to Ground). User can
Table 3 Oscillator Modes as defined by FSMD, FMMD1, FMMD0.
Table 4 Summary of maximum operating speeds
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:
FSMD
Internal capacitor mode (ERIC)
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.
0
0
0
1
1
1
Conditions
Two clocks
FMMD1
0
0
1
0
0
1
FMMD0
0
1
×
0
1
×
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)
Main Clock
Product Specification (V1.6) 12.31.2007
Fxt Max. (MHz)
10
4
8
RC type (ERIC)
RC type (ERIC)
RC type (ERIC)
Crystal type
Crystal type
Crystal type
Sub-clock