HD6417660 RENESAS [Renesas Technology Corp], HD6417660 Datasheet - Page 656

• Manufacturer Part Number: HD6417660
• Description: Renesas 32-Bit RISC Microcomputer
• Manufacturer: RENESAS [Renesas Technology Corp]

21.6
This BT has an interface to receive an external clock running at 32 kHz or 32.768 kHz to support
Bluetooth’s power-down modes (Sniff, Park, and Hold). There are four ways to supply this low-
frequency clock (described below). The method is specified by the value of the RTCSEL1 bit in
the PSELA. For details on the PSELA, refer to section 24, Pin Function Controller (PFC).
Here are the five possible ways to obtain the low-frequency clock signal;
• connect the 32-kHz crystal resonator to the EXTAL2 and XTAL2 pins to make the on-chip
• connect the 32.768-kHz crystal resonator to the EXTAL2 and XTAL2 pins to make the on-
• directly input 32.0-kHz from the EXTAL2 pin; and
• directly input 32.768-kHz from the EXTAL2 pin, and generate the pseudo 32-kHz clock in the
Table 21.2 is a list of the settings.
Table 21.2 Settings and Functions
21.6.1
The RTCSEL1 bit in the PSELA selects whether or not the frequency-conversion circuit is
activated. The frequency-conversion circuit generates a pseudo-32-kHz clock signal from a
32.768-kHz signal. Activating the frequency-conversion circuit allows the use of the 32.768-kHz
crystal resonator, as used with the RTC (Real Time Clock), instead of the connection of a 32.0-
kHz crystal resonator to the EXTAL2 and XTAL2 pins.
Clearing the RTCSEL1 bit to 0 activates the frequency-conversion circuit. Setting the RTCSEL1
bit makes the circuit inactive and the 32.768-kHz frequency is passed through the circuit. When
the RTCSEL0 pin is set to 1, the RTCSEL1 bit should always be set to 1. The initial value of the
RTCSEL1 bit is 0. For details on the PSELA, refer to section 24, Pin Function Controller (PFC).
Rev. 1.00, 02/04, page 618 of 804
RTCSEL1 Bit
1
0
oscillator circuit provide the clock;
chip oscillation circuit provide the clock of 32.768kHz, and generate the pseudo 32-kHz clock
in the frequency-conversion circuit;
frequency-conversion circuit.
Low-Frequency Clock Oscillator Interface
Using RTCSEL1 Bit to Select Clock Function
Function
The 32-kHz crystal resonator is connected to the EXTAL2 and XTAL2 pins to
make the on-chip oscillation circuit provide a signal. If not, 32.0-kHz clock
should be supplied at the EXTAL2 pin.
The 32.768-kHz crystal resonator is connected to the EXTAL2 and XTAL2
pins to make the on-chip oscillation circuit provide a signal. If not, 32.768-kHz
clock should be supplied at the EXTAL2 pin.