
M44C510E
Rev. A1, 04-May-00
Preliminary Information
16 (60)
System Configuration Register (SC)
Primary register address: ’E’hex
Bit 3
Bit 2
Bit 1
Bit 0
SC: write
RC1
RC0
OS1
OS0
Reset value: 1111b
RC1, RC0
Internal RC oscillator 1 frequency select (SYSCLmax)
RC1
RC0
SYSCLmax @ 25
°C, VDD = 5 V
Note
0
0
7.0 MHz (fiRC0)
0
1
3.0 MHz (fiRC1)
1
0
2.0 MHz (fiRC2)
1
1
0.8 MHz (fiRC3)
Reset value
OS1, OS0
Oscillator selection bits (in conjunction with the CCS-bit)
CCS
OS1
OS0
SUBCL
System Oscillator Selection
0
1
1
External input clock at SCLIN
0
0
1
SYSCLmax/64
RC-oscillator 2 with Rext
0
1
0
4-MHz crystal oscillator
0
0
0
32 kHz
32-kHz crystal oscillator
1
x
x
SYSCLmax/64 or 32 kHz
RC-oscillator 1
If CCS = 0 in the CM-register, the RC-oscillator 1 is stopped.
1.5.4
Power-down Modes
The M44C510E encorporates several modes which en-
able the power consumption to be tailored to a minimum
without sacrificing computational power. When the con-
troller exits the lowest priority interrupt task, it reverts to
a SLEEP state. This is a CPU shutdown condition which
is used to reduce average system power consumption
where the CPU itself is only partially utilized. In SLEEP,
the CPU clocking system is deactivated whereby the pe-
ripherals and associated clock sources may remain active
(Standby Mode) or they can also be halted (Halt Mode).
In Standby Mode, the peripherals are able to continue op-
eration and if required also generate interrupts which can,
along with a reset reactivate the CPU to bring it out of the
sleep state.
SLEEP can only be maintained when none of the interrupt
pending or active register bits are set. The application of
the $AUTOSLEEP routine ensures the correct function of
the sleep mode.
In both Standby and Active modes the current consump-
tion is largely dependent on the frequency of the CPU
system clock (SYSCL) and the supply voltage (VDD).
(see figures 48 and 49) while the Halt Mode current is
merely controller static leakage current.
Selection of Standby or Halt mode is performed by the
NSTOP bit in the clock managent register (CM). It should
be noted that the low power 32-kHz crystal oscillator, if
enabled will always remain active in both Standby and
Halt modes.
Table 6. Power-down modes
Mode
CPU Core
State
NSTOP
RC-Oscillator 1
RC-Oscillator 2
4-MHz Oscillator
32-kHz Oscillator
External Input
Clock at SCLIN
Active
RUN
1
RUN
RUN
Enabled
Standby
SLEEP
1
RUN
RUN
Enabled
Halt
SLEEP
0
STOP
RUN
Disabled