UPD78F1502AGK-GAK-AX Datasheet, PDF (980/1031 Pages) Renesas Technology Corp – 16-Bit Single-Chip Microcontrollers

78K0R/Lx3
Function
Details of
Function
APPENDIX C LIST OF CAUTIONS
Cautions
(8/39)
Page
Clock
OSMC:
To shift to STOP mode while VDD ≤ 2.7 V, set FSEL = 0 after setting fCLK to 10 MHz or p.221 _†
generator Operation speed less.
mode control
The HALT mode current when operating on the subsystem clock can be reduced by p.221 _†
register
setting RTCLPC to 1. However, the clock cannot be supplied to peripheral functions
except the real-time counter in the subsystem clock HALT mode. Set bit 7 (RTCEN)
of PER0 to 1 and bits 0 to 6 of PER0 to 0 before setting the subsystem clock HALT
mode.
Once FLPC has been set from 0 to 1, setting it back to 0 from 1 other than by reset is p.221 _†
prohibited.
When setting FSEL to “1”, do so while RMC = 00H.
p.221 _†
When setting FLPC to “1”, do so while RMC = 5AH.
X1/XT1
−
When using the X1 oscillator and XT1 oscillator, wire as follows in the area enclosed p.223 _†
oscillator
by the broken lines in the Figures 5-10 and 5-11 to avoid an adverse effect from
wiring capacitance.
• Keep the wiring length as short as possible.
• Do not cross the wiring with the other signal lines. Do not route the wiring near a
signal line through which a high fluctuating current flows.
• Always make the ground point of the oscillator capacitor the same potential as VSS.
Do not ground the capacitor to a ground pattern through which a high current flows.
• Do not fetch signals from the oscillator.
Note that the XT1 oscillator is designed as a low-gain circuit for achieving low-power
consumption. Note the following points when designing the XT1 oscillator.
• The pins and circuit board include parasitic capacitance. Therefore, confirm that
there are no problems by performing oscillation evaluation on the circuit board to
be actually used.
• When low-consumption oscillation or super-low-consumption oscillation is selected,
lower power consumption than when selecting normal oscillation can be achieved.
However, in this case, the XT1 oscillation margin is reduced, so perform sufficient
oscillation evaluation of the resonator to be used for XT1 oscillation before using
the resonator.
• Keep the wiring length between the XT1 and XT2 pins and resonator as short as
possible and parasitic capacitance and wire resistance as small as possible. This
is particularly important when super-low-consumption oscillation (AMPHS1 = 1) is
selected.
• Configure the circuit board by using material with little parasitic capacitance and
wire resistance.
• Place a ground pattern that has the same potential as VSS (if possible) around the
XT1 oscillator.
• Do not cross the signal lines between the XT1 and XT2 pins and the resonator with
other signal lines. Do not route the signal lines near a signal line through which a
high fluctuating current flows.
• Moisture absorption by the circuit board and condensation on the board in a highly
humid environment may cause the impedance between the XT1 and XT2 pins to
drop and disable oscillation. When using the circuit board in such an environment,
prevent the circuit board from absorbing moisture by taking measures such as
coating the circuit board.
• Coat the surface of the circuit board by using material that does not generate
capacitance or leakage between the XT1 and XT2 pins.
R01UH0004EJ0501 Rev.5.01
964
Jun 20, 2011