CHAPTER 5 CLOCK GENERATORS
User’s Manual U16898EJ3V0UD
78
Figure 5-11. Status Transition of Default Start by Crystal/Ceramic Oscillation
HALT
STOP
HALT
instruction
STOP
instruction
V
DD
> 2.1 V
±
0.1 V
Start with PCC = 02H,
PPCC = 02H
Interrupt
Reset signal
Interrupt
Power
application
Clock division ratio
variable during
CPU operation
Wait for clock
oscillation stabilization
Crystal/ceramic
oscillation selected
by option byte
Reset by
power-on clear
Remark
PCC: Processor clock control register
PPCC: Preprocessor clock control register
(3) External clock input circuit
If external clock input is selected by the option byte, the following is possible.
•
High-speed operation
The accuracy of processing is improved as compared with high-speed internal oscillation (8 MHz (TYP.))
because an oscillation frequency of 1 to 10 MHz can be selected and an external clock with a small frequency
deviation can be supplied.
•
Improvement of expandability
If the external clock input circuit is selected as the oscillator, the X2 pin can be used as an I/O port pin. For
details, refer to
CHAPTER 4 PORT FUNCTIONS
.
Figures 5-12 and 5-13 show the timing chart and status transition diagram of default start by external clock input.