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Limitation point on the use of DFM
1. it's prohibited to execute DFM enable/disable control in the SLOW mode (fs). You
should control DFM in the NORMAL mode.
2. If you stop DFM operation during using DFM (DFMCR0<ACT1:0> = "10"), you
shouldn't execute the commands that change the clock f
DFM at the same time. Therefore the above execution should be separated into
two procedures as showing below.
LD
(DFMCR0), C0H
LD
(DFMCR0), 00H
3. If you stop high-frequency oscillator during using DFM (DFMCR0<ACT1:0> =
"10"), you should stop DFM before you stop high-frequency oscillator.
4. More than 1 ms of interval time is required from stop of DFM to the next start up
of DFM.
Examples of settings are below.
(1)
Start up control
(OK) Low-frequency oscillator operation mode (fs) (High-frequency oscillator STOP)
→ High-frequency oscillator start up → High-frequency oscillator operation mode
(f
) → DFM start up → DFM use mode (f
OSCH
LD
(SYSCR0), 11---1--B
WUP:
BIT
2, (SYSCR0)
JR
NZ, WUP
LD
(SYSCR1), ----0---B
LD
(DFMCR0), 01-0----B
LUP:
BIT
5, (DFMCR0)
JR
NZ, LUP
LD
(DFMCR0), 10-0----B
(OK) Low-frequency oscillator operation mode (fs) (High-frequency oscillator operate)
→ High-frequency oscillator operation mode (f
mode (f
)
DFM
LD
(SYSCR1), ----0---B
LD
(DFMCR0), 01-0----B
LUP:
BIT
5, (DFMCR0)
JR
NZ, LUP
LD
(DFMCR0), 10-0----B
(Error) Low-frequency oscillator operation mode (fs) (High-frequency oscillator STOP)
→ High-frequency oscillator start up → DFM start up → DFM use mode (f
LD
(SYSCR0), 11---1--B
WUP:
BIT
2, (SYSCR0)
JR
NZ, WUP
LD
(DFMCR0), 01-0----B
LUP:
BIT
5, (DFMCR0)
JR
NZ, LUP
LD
(DFMCR0), 10-0----B
LD
(SYSCR1), ----0---B
;
Change the clock f
;
DFM stop
)
DFM
;
High-frequency oscillator start up/warm-up start
;
Check for the flag of warm-up end
;
;
Change the system clock fs to f
;
DFM start up/lockup start
;
Check for the flag of lockup end
;
;
Change the system clock f
OSCH
;
Change the system clock fs to f
;
DFM start up/lockup start
;
Check for the flag of lockup end
;
;
Change the system clock f
;
High-frequency oscillator start up/warm-up start
;
Check for the flag of warm-up end
;
;
DFM start up/lockup start
;
Check for the flag of lockup end
;
;
Change the clock f
;
Change the internal clock fs to f
91C824-23
TMP91C824
to f
and stop the
DFM
OSCH
to f
DFM
OSCH
OSCH
to f
OSCH
DFM
) → DFM start up → DFM use
OSCH
to f
OSCH
DFM
)
DFM
to f
OSCH
DFM
DFM
2008-02-20
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