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Advance Information
UM-TM57PE10_E
8-Bit Microcontroller
17
tenx technology inc.
Preliminary
Rev 1.4, 2012/01/19
2.5 Dual System Clock
TM57PE10 is designed with dual-clock system. There are five kinds of clock source, FXT (Fast Crystal)
Clock, SXT (Slow Crystal) Clock, XRC (External RC) Clock, SIRC (Slow Internal RC) Clock and FIRC
(Fast Internal RC). Each clock source can be applied to CPU kernel as system clock. When in idle mode,
only slow clock can be configured to keep oscillating to provide clock source to Timer2. Refer to the
Figure as below.
SYSCFG[9:8]
Fast Clock
SUBTYP[1:0]
Slow Clock
Clock
Switch
To CPU
Divide
by 128
Timer2
TM2CLK
1
0
SELSUB
10
XRC
01
SIRC
00
SXT
00
XRC
01
FIRC
10
SXT
11
FXT
Fast Mode:
After power on or reset, TM57PE10 enters fast mode. In fast mode, TM57PE10 can select FXT, XRC or
FIRC as its CPU clock by SYSCFG bit9 and bit8 setting. Besides, firmware can also enable or disable
the slow clock for the Timer2 system operating. In this mode, the program is executed using fast clock
as CPU clock. The Timer0, PWM0, PWM1 blocks are also driven by fast clock. Timer2 can also be
driven by fast clock by setting TM2CLK to “1”.
Slow Mode:
In slow mode, TM57PE10 can select SXT, XRC or SIRC as its CPU clock by R-Plane control register
(SUBTYP). In this mode, the fast clock is stopped and slow clock is enabled for power saving. All
peripheral blocks clock sources are slow clock in the slow mode.
IDLE Mode:
If slow clock is enabled and TM2CLK=0 before executing the SLEEP instruction, the TM57PE10 enters
the “Idle Mode”. In this mode, the slow clock will continue running to provide clock to Timer2 block. CPU
stop fetching code and all blocks are stop except Timer2 related circuits.
Stop Mode:
If slow clock is disabled before executing the SLEEP instruction, every block is turned off and the
TM57PE10 enters the “Stop Mode”. Stop mode is similar to idle mode. The difference is all clock
oscillators either fast or slow is powered-down and no clock is generated.