M37517F8HP Datasheet, PDF (52/98 Pages) Renesas Technology Corp – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

7517 Group
Oscillation Control
(1) Stop mode
If the STP instruction is executed, the internal clock φ stops at an
“H” level, and high-speed on-chip oscillation clock or XIN and XCIN
oscillation stops. When the oscillation stabilizing time set after
STP instruction released bit is “0”, the prescaler 12 is set to “FF16”
and timer 1 is set to “0116”. When the oscillation stabilizing time
set after STP instruction released bit is “1”, set the sufficient time
for oscillation of used oscillator to stabilize since nothing is set to
the prescaler 12 and timer 1.
Either high-speed on-chip oscillation clock, or XIN or XCIN divided
by 16 is input to the prescaler 12 as count source. Oscillator re-
starts when an external interrupt is received, but the internal clock
φ is not supplied to the CPU (remains at “H”) until timer 1
underflows. The internal clock φ is supplied for the first time, when
timer 1 underflows. This ensures time for the clock oscillation us-
ing the ceramic resonators to be stabilized. When the oscillator is
____________
restarted by reset, apply “L” level to the RESET pin until the oscil-
lation is stable since a wait time will not be generated.
In case of using high-speed on-chip oscillation clock as main
clock, the oscillation stabilizing time does not almost need.
(2) Wait mode
If the WIT instruction is executed, the internal clock φ stops at an
“H” level, but the oscillator does not stop. The internal clock φ re-
starts at reset or when an interrupt is received. Since the oscillator
does not stop, normal operation can be started immediately after
the clock is restarted.
To ensure that the interrupts will be received to release the STP or
WIT state, their interrupt enable bits must be set to “1” before ex-
ecuting of the STP or WIT instruction.
When releasing the STP state, the prescaler 12 and timer 1 will
start counting the high-speed on-chip oscillation clock or XIN di-
vided by 16. Accordingly, set the timer 1 interrupt enable bit to “0”
before executing the STP instruction.
sNote
When using XIN-XOUT oscillation by using an external resonator, in
case of using the oscillation stabilizing time set after STP instruc-
tion released bit set to “1”, evaluate time to stabilize oscillation of
the used oscillator and set the value to the timer 1 and prescaler
12.
XCIN XCOUT XIN XOUT
Rf _Rd
CCIN CCOUT CIN COUT
Fig. 57 Ceramic resonator circuit
XCIN XCOUT XIN XOUT
Rf
CCIN
Open
Rd
External oscillation
circuit
CCOUT
Vcc
Vss
Fig. 58 External clock input circuit
XCIN XCOUT
XIN XOUT
82kΩ
120pF
Open Open
Fig.59 On-chip oscillation circuit and 32kHz CR oscillation
circuit
Rev.1.01 Aug 02, 2004 page 52 of 96