
CHAPTER 6 CLOCK GENERATION FUNCTION
User
’
s Manual U15862EJ3V0UD
299
6.4 Operation
6.4.1 Operation of each clock
The following table shows the operation status of each clock.
Table 6-1. Operation Status of Each Clock
CLK bit = 0, MCK bit = 0
CLS bit = 1,
MCK bit = 0
CLS bit = 1,
MCK bit = 1
<1>
<2>
<3>
<4>
<5>
<6>
<7>
<6>
<7>
Main clock oscillator (f
X
)
×
{
{
{
×
{
{
×
×
Subclock oscillator (f
XT
)
{
{
{
{
{
{
{
{
{
CPU clock (f
CPU
)
×
×
×
×
×
{
×
{
×
Internal system clock (f
CLK
)
×
×
{
×
×
{
×
{
×
Peripheral clock (f
XX
to f
XX
/1024)
×
×
{
×
×
{
×
×
×
WT clock (main)
×
{
{
{
×
{
{
×
×
WT clock (sub)
{
{
{
{
{
{
{
{
{
WDT1 clock (f
XW
)
×
{
{
{
×
{
{
×
×
WDT2 clock (main)
×
×
{
×
×
{
×
×
×
WDT2 clock (sub)
{
{
{
{
{
{
{
{
{
Remark
CLS bit:
MCK bit: Bit 6 of the PCC register
O:
Operable
×
:
Stopped
<1>: RESET pin input
<2>: During oscillation stabilization time count
<3>: HALT mode
<4>: IDLE mode
<5>: STOP mode
<6>: Subclock operation mode
<7>: Sub-IDLE mode
Bit 4 of the processor clock control register (PCC)
6.4.2 Clock output function
The clock output function is used to output the internal system clock (f
CLK
) from the CLKOUT pin.
The internal system clock (f
CLK
) is selected by using the CK3 to CK0 bits of the processor clock control register
(PCC).
The CLKOUT pin functions alternately as the PCM1 pin and functions as a clock output pin if so specified by the
control register of port CM.
The status of the CLKOUT pin is the same as the internal system clock in Table 6-1 and the pin can output the
clock when it is in the operable status. It outputs a low level in the stopped status. However, the alternate-function
pin function (PCM1: input mode) is selected in <1> and <2> after the RESET signal has been input. Consequently,
the CLKOUT pin goes into a high-impedance state.
6.4.3 External clock input function
An external clock can be directly input to the oscillator. Input the clock to the X1 pin and its inverse signal to the X2
pin. Set the MFRC bit of the PCC register to 1 (to cut off the feedback resistor). Note, however, that oscillation
stabilization time is inserted even in the external clock mode.