NEC 78K0S/KA1+ Preliminary User's Manual page 75

www.DataSheet4U.com
www.DataSheet4U.com
Remark PCC:
(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 Ring-OSC oscillation (8 MHz (TYP.))
because an oscillation frequency of 500 kHz 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 5-14 and 5-15 show the timing chart and status transition diagram of default start by external clock input.
CHAPTER 5 CLOCK GENERATORS
Figure 5-13. Status Transition of Default Start by Crystal/Ceramic Oscillation
Crystal/ceramic
oscillation selected
oscillation stabilization
Clock division ratio
Interrupt
instruction
HALT
Processor clock control register
PPCC: Preprocessor clock control register
Preliminary User's Manual U16898EJ1V0UD
Power
application
> 2.1 V ±0.1 V
V
DD
Reset by
power-on clear
by option byte
Start with PCC = 02H,
PPCC = 02H
Wait for clock
variable during
CPU operation
Interrupt
HALT
STOP
instruction
STOP
Reset signal
75