HD6417750RF240DV Datasheet, PDF(386/1132 Page) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH™ RISC engine Family / SH7750 Series

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HD6417750RF240DV Datasheet, PDF (386/1132 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH™ RISC engine Family / SH7750 Series

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Section 11 Realtime Clock (RTC)

SH7750, SH7750S, SH7750R Group

VDD-RTC

SH7750

SH7750S

SH7750R

Rf

VSS-RTC

EXTAL2

RD

XTAL2

Noise filter

CRTC

RRTC

3.3 V

XTAL

Cin

Cout

Notes: 1. Select either the Cin or Cout side for the frequency adjustment variable capacitor according to

requirements such as the adjustment range, degree of stability, etc.

2. Built-in resistance value Rf (typ. value) = 10 MÎ©, RD (typ. value) = 400 kÎ©

3. Cin and Cout values include floating capacitance due to the wiring. Take care when using a solid-

earth board.

4. The crystal oscillation stabilization time depends on the mounted circuit constants, floating

capacitance, etc., and should be decided after consultation with the crystal resonator

manufacturer.

5. Place the crystal resonator and load capacitors Cin and Cout as close as possible to the chip.

(Correct oscillation may not be possible if there is externally induced noise in the EXTAL2 and

XTAL2 pins.)

6. Ensure that the crystal resonator connection pin (EXTAL2 and XTAL2) wiring is routed as far away

as possible from other power lines (except GND) and signal lines.

7. Insert a noise filter in the RTC power supply.

Figure 11.5 Example of Crystal Oscillator Circuit Connection

11.5.4 RTC Register Settings (SH7750 only)

Description: When setting values are written to an RTC register, values may change in writable

RTC counter registers other than that to which the settings are written.

The RTC registers are R64CNT, RSECCNT, RMINCNT, RHRCNT, RWKCNT, RDAYCNT,

RMONCNT, RYRCNT, RSECAR, RMINAR, RHRAR, RDAYAR, RWKAR, RMONAR, RCR1,

and RCR2. Of these, RSECCNT, RMINCNT, RHRCNT, RWKCNT, RDAYCNT, RMONCNT,

and RYRCNT are writeable registers.

Workarounds: To avoid the problem, use one of methods 1. to 3. below to write settings to the

RTC registers.

1. Disable the DMAC channels used to access peripheral registers before writing to an RTC

register, and write to the RTC register while the exception/interrupt block bit (SR.BL) in the

status register is set to 1. Then use the next instruction to read from the same register.

Page 334 of 1076

R01UH0456EJ0702 Rev. 7.02

Sep 24, 2013

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