E0C6006 TECHNICAL MANUAL
EPSON
13
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Oscillation Circuit)
V
DD
OSC4
OSC3
C
DC
C
GC
OSCC
Ceramic
To CPU and
REM circuit
R
FC
R
DC
(b) Ceramic oscillation circuit
OSC4
OSC3
V
DD
V
S1
(c) When "Not Use" is selected by mask option
Fig. 4.3.3.1 OSC3 oscillation circuit
As shown in Figure 4.3.3.1, the CR oscillation circuit can be configured simply by connecting the resistor
R
CR
between the OSC3 and OSC4 terminals when CR oscillation is selected. See Chapter 6, "Electrical
Characteristics" for resistance value of R
CR
.
When ceramic oscillation is selected, the ceramic oscillation circuit can be configured by connecting the
ceramic oscillator (Typ. 455 kHz) between the OSC3 and OSC4 terminals, capacitor C
GC
between the
OSC3 and V
DD
terminals, and capacitor C
DC
between the OSC4 and V
DD
terminals. For both C
GC
and
C
DC
, connect capacitors that are about 100 pF.
The OSC3 ocsillation circuit can be controlled (on and off) using the OSCC register. To reduce current
consumption, the OSC3 oscillation circuit should be stopped by the software (OSCC register) if unneces-
sary.
When "Not Use" is selected by mask option, do not connect anything to the OSC3 and OSC4 terminals.
4.3.4 Switching the system clock
The CPU system clock is switched to OSC1 or OSC3 by the software (CLKCHG register).
When OSC3 is to be used as the CPU clock, it should be done as the following procedure using the
software: turn the OSC3 oscillation ON and wait at least 5 msec for oscillation stabilization, then switch
the CPU clock after waiting 5 msec or more.
When switching from OSC3 to OSC1, switch the CPU clock, then turn the OSC3 oscillation circuit off.
OSC1
→
OSC3
OSC3
→
OSC1
1. Set OSCC to "1" (OSC3 oscillation ON).
1. Set CLKCHG to "0" (OSC3
→
OSC1).
2. Maintain 5 msec or more.
2. Set OSCC to "0" (OSC3 oscillation OFF).
3. Set CLKCHG to "1" (OSC1
→
OSC3).
4.3.5 Clock frequency and instruction execution time
Table 4.3.5.1 shows the instruction execution time according to each frequency of the system clock.
Table 4.3.5.1 Clock frequency and instruction execution time
Clock frequency
OSC1: 32.768 kHz
OSC3: 455 kHz
5-clock instruction
152.6
11.0
7-clock instruction
213.6
15.4
12-clock instruction
366.2
26.4
Instruction execution time (
µ
sec)