EM78468
8-BIT Microcontroller
4.6 Oscillator
4.6.1 Oscillator Modes
This LSI can operate in the three different oscillator modes from main oscillator (R-OSCI,
OSCO), such as RC oscillator with external resistor and Internal capacitor mode (ERIC);
crystal oscillator mode; and PLL operation mode (R-OSCI connected 0.01μF capacitor
to Ground). User can select one of them 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
1
1
1
0
0
1
0
0
1
0
1
X
0
1
X
RC type (ERIC)
Crystal type
PLL type
RC type (ERIC)
Crystal type
PLL type
RC type (ERIC)
RC type (ERIC)
RC type (ERIC)
Crystal type
Crystal type
Crystal type
Table 4 Summary of maximum operating speeds
Conditions
VDD
Fxt max.(MHz)
2.3
3.0
4
8
Two clocks
5.0
10
4.6.2 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:
R-OSCI
Xin
C1
XTAL
Xout
Rs
C2
Circuit for PLL mode
36 •
Product Specification (V1.1) 04.11.2005
(This specification is subject to change without further notice)
ELAN [ ELAN MICROELECTRONICS CORP ]
