Datasheet
Table Of Contents
- Notes regarding these materials
- General Precautions in the Handling of MPU/MCU Products
- How to Use This Manual
- Table of Contents
- Quick Reference by Address B-
- 1. Overview
- 2. Central Processing Unit (CPU)
- 2.1 Data Registers (R0, R1, R2 and R3)
- 2.2 Address Registers (A0 and A1)
- 2.3 Frame Base Register (FB)
- 2.4 Interrupt Table Register (INTB)
- 2.5 Program Counter (PC)
- 2.6 User Stack Pointer (USP) and Interrupt Stack Pointer (ISP)
- 2.7 Static Base Register (SB)
- 2.8 Flag Register (FLG)
- 2.8.1 Carry Flag (C Flag)
- 2.8.2 Debug Flag (D Flag)
- 2.8.3 Zero Flag (Z Flag)
- 2.8.4 Sign Flag (S Flag)
- 2.8.5 Register Bank Select Flag (B Flag)
- 2.8.6 Overflow Flag (O Flag)
- 2.8.7 Interrupt Enable Flag (I Flag)
- 2.8.8 Stack Pointer Select Flag (U Flag)
- 2.8.9 Processor Interrupt Priority Level (IPL)
- 2.8.10 Reserved Area
- 3. Memory
- 4. Special Function Registers (SFRs)
- 5. Reset
- 6. Processor Mode
- 7. Clock Generation Circuit
- 8. Protection
- 9. Interrupt
- 10. Watchdog Timer
- 11. DMAC
- 12. Timer
- 13. Serial I/O
- 14. A/D Converter
- 15. CRC Calculation Circuit
- 16. Programmable I/O Ports
- 16.1 Port Pi Direction Register (PDi Register, i = 1, 6 to 10)
- 16.2 Port Pi Register (Pi Register, i = 1, 6 to 10)
- 16.3 Pull-up Control Register 0 to Pull-up Control Register 2 (PUR0 to PUR2 Registers)
- 16.4 Port Control Register
- 16.5 Pin Assignment Control register (PACR)
- 16.6 Digital Debounce function
- 17. Flash Memory Version
- 17.1 Flash Memory Performance
- 17.2 Memory Map
- 17.3 Functions To Prevent Flash Memory from Rewriting
- 17.4 CPU Rewrite Mode
- 17.5 Register Description
- 17.6 Precautions in CPU Rewrite Mode
- 17.6.1 Operation Speed
- 17.6.2 Prohibited Instructions
- 17.6.3 Interrupts
- 17.6.4 How to Access
- 17.6.5 Writing in the User ROM Space
- 17.6.6 DMA Transfer
- 17.6.7 Writing Command and Data
- 17.6.8 Wait Mode
- 17.6.9 Stop Mode
- 17.6.10 Low Power Consumption Mode and On-chip Oscillator-Low Power Consumption Mode
- 17.7 Software Commands
- 17.8 Status Register
- 17.9 Standard Serial I/O Mode
- 17.10 Parallel I/O Mode
- 18. Electrical Characteristics
- 19. Usage Notes
- 19.1 SFR
- 19.2 PLL Frequency Synthesizer
- 19.3 Power Control
- 19.4 Protect
- 19.5 Interrupts
- 19.6 DMAC
- 19.7 Timer
- 19.8 Serial I/O
- 19.9 A/D Converter
- 19.10 Programmable I/O Ports
- 19.11 Electric Characteristic Differences Between Mask ROM
- 19.12 Mask ROM Version
- 19.13 Flash Memory Version
- 19.13.1 Functions to Inhibit Rewriting Flash Memory
- 19.13.2 Stop mode
- 19.13.3 Wait mode
- 19.13.4 Low power dissipation mode, on-chip oscillator low power dissipation mode
- 19.13.5 Writing command and data
- 19.13.6 Program Command
- 19.13.7 Operation speed
- 19.13.8 Instructions prohibited in EW0 Mode
- 19.13.9 Interrupts
- 19.13.10 How to access
- 19.13.11 Writing in the user ROM area
- 19.13.12 DMA transfer
- 19.13.13 Regarding Programming/Erasure Times and Execution Time
- 19.13.14 Definition of Programming/Erasure Times
- 19.13.15 Flash Memory Version Electrical Characteristics 10,000 E/W cycle product
- 19.13.16 Boot Mode
- 19.14 Noise
- 19.15 Instruction for a Device Use
- Appendix 1. Package Dimensions
- Appendix 2. Functional Difference
- Register Index
- REVISION HISTORY

7. Clock Generation Circuit
page 45
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Figure 7.1.1. Examples of Main Clock Connection Circuit
The following describes the clocks generated by the clock generation circuit.
7.1 Main Clock
The main clock is generated by the main clock oscillation circuit. This clock is used as the clock source for
the CPU and peripheral function clocks. The main clock oscillator circuit is configured by connecting a
resonator between the XIN and XOUT pins. The main clock oscillator circuit contains a feedback resistor,
which is disconnected from the oscillator circuit during stop mode in order to reduce the amount of power
consumed in the chip. The main clock oscillator circuit may also be configured by feeding an externally
generated clock to the XIN pin. Figure 7.1.1 shows the examples of main clock connection circuit.
The main clock after reset oscillates in the M16C/26A and M16C/26B, but stop in the M16C/26T.
The power consumption in the chip can be reduced by setting the CM05 bit in the CM0 register to “1” (main
clock oscillator circuit turned off) after switching the clock source for the CPU clock to a sub clock or on-chip
oscillator clock. In this case, XOUT goes “H”. Furthermore, because the internal feedback resistor remains
on, XIN is pulled “H” to XOUT via the feedback resistor.
During stop mode, all clocks including the main clock are turned off. Refer to 7.6 power control.
If the main clock is not used, it is recommended to connect the XIN pin to VCC to reduce power consump-
tion during reset.
External Clock
XIN
XOUT
Open
V
CC
V
SS
NOTE:
1. Insert a damping resistor if required. Resistance value varies depending on the oscillator setting.
Use resistance value recommended by the oscillator manufacturer. If the oscillator manufacturer
recommends that a feedback resistor be added to the chip externally, insert a feedback resistor
between X
IN
and X
OUT
.
2. The external clock should not be stopped when it is connected to the X
IN
pin and the main clock is
selected as the CPU clock.
Oscillator
Rd
(1)
C
IN
C
OUT
X
IN
X
OUT
MCU
(Built-in Feedback Resistor)
MCU
(Built-in Feedback Resistor)
V
SS