Toshiba TMP91C815F Data Book page 28

3.3.6 Noise reduction circuits
Noise reduction circuits are built in, allowing implementation of the following features.
(1) Reduced drivability for high-frequency oscillator
(2) Reduced drivability for low-frequency oscillator
(3) Single drive for high-frequency oscillator
(4) SFR protection of register contents
(5) ROM protection of register contents
(6) Release from hard protection
The above functions are performed by making the appropriate settings in the EMCCR0
to EMCCR3 registers.
(1) Reduced drivability for high-frequency oscillator
(Purpose)
Reduces noise and power for oscillator when a resonator is used.
(Block diagram)
C1
resonator
C2
(Setting method)
The drivability of the oscillator is reduced by writing"0" to EMCCR0<DRVOSCH> register. By
reset, <DRVOSCH> is initialized to "1" and the oscillator starts oscillation by normal-drivability
when the power-supply is on.
X1 pin
XT2 pin
91C815-25
f
OSCH
Enable oscillation (STOP+EMCCR0<EXTIN>)
EMCCR0<DRVOSCH>
TMP91C815