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Clock Generator
(2)
Access
Address
Initial Value
Table 4-5
Bit position
Bit name
1
MCS
0
MCM0
MCM - Main system clock mode register
The 8-bit MCM register specifies the main system clock (f
through mode and informs about its status.
This register can be read/written in 1-bit or 8-bit units.
Writing to this register is protected by a special sequence of instructions.
Please refer to "CPU System Functions" on page 135 for details.
FFFF F860
.
H
00
. The register is initialized by any reset.
H
7
6
5
0
0
0
R
R
R
MCM register contents
Status of the main system clock f
0: Operating on 8 MHz internal oscillator clock f
1: Operating on MainOSC clock f
Clock selection of main system clock f
0: Clock source is the 8 MHz internal oscillator f
1: Clock source is
– MainOSC f
(in clock-through mode, if PLLCTL.SELPLL = 0)
X
– PLL output f
(in PLL mode, if PLLCTL.SELPLL = 1)
PLL
Caution: 1.
When the oscillation of a previous clock switch is not steady, rewriting
of this bit is prohibited.
2.
The MCM0 can be set to 0 only, if the current mode is clock-through,
i.e. PLLCTL.SELPLL = 0. Do not change from PLL mode or subclock
operation mode directly to 8 MHz internal oscillator clock-through
mode or vice versa.
User's Manual U18743EE1V2UM00
4
3
2
0
0
0
R
R
R
Function
(in clock-through mode, if PLLCTL.SELPLL = 0):
XX
RH
.
X
:
XX
RH
Chapter 4
) source in clock-
XX
1
0
MCS
MCM0
R
R/W
.
(in clock-through mode).
169
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