Oscillator; Oscillator Modes; Phase Lock Loop (Pll Mode) - IBM MiEM78P468L Product Specification

EM78P468N/EM78P468L
8-Bit Microcontroller

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 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.
FSMD
0
0
0
1
1
1
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:
30 •
FMMD1 FMMD0
0 0
0 1
×
1
0 0
0 1
×
1
Conditions
Two clocks
R-OSCI
Xin
EM78P468N
Xout
Fig. 6-6 PLL Mode Circuit
Main Clock
RC type (ERIC)
Crystal type
PLL type
RC type (ERIC)
Crystal type
PLL type
VDD Fxt Max. (MHz)
2.3 4
3.0 8
5.0 10
0.01uF
C1
XTAL
C2
Product Specification (V1.5) 02.15.2007
(This specification is subject to change without further notice)
Sub-clock
RC type (ERIC)
RC type (ERIC)
RC type (ERIC)
Crystal type
Crystal type
Crystal type