R8C2C datasheet(3/58 Pages) RENESAS

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General Precautions in the Handling of MPU/MCU Products

The following usage notes are applicable to all MPU/MCU products from Renesas. For detailed usage notes

on the products covered by this manual, refer to the relevant sections of the manual. If the descriptions under

General Precautions in the Handling of MPU/MCU Products and in the body of the manual differ from each

other, the description in the body of the manual takes precedence.

1. Handling of Unused Pins

Handle unused pins in accord with the directions given under Handling of Unused Pins in the

manual.

 The input pins of CMOS products are generally in the high-impedance state. In operation

with an unused pin in the open-circuit state, extra electromagnetic noise is induced in the

vicinity of LSI, an associated shoot-through current flows internally, and malfunctions occur

due to the false recognition of the pin state as an input signal become possible. Unused

pins should be handled as described under Handling of Unused Pins in the manual.

2. Processing at Power-on

The state of the product is undefined at the moment when power is supplied.

 The states of internal circuits in the LSI are indeterminate and the states of register

settings and pins are undefined at the moment when power is supplied.

In a finished product where the reset signal is applied to the external reset pin, the states

of pins are not guaranteed from the moment when power is supplied until the reset

process is completed.

In a similar way, the states of pins in a product that is reset by an on-chip power-on reset

function are not guaranteed from the moment when power is supplied until the power

reaches the level at which resetting has been specified.

3. Prohibition of Access to Reserved Addresses

Access to reserved addresses is prohibited.

 The reserved addresses are provided for the possible future expansion of functions. Do

not access these addresses; the correct operation of LSI is not guaranteed if they are

accessed.

4. Clock Signals

After applying a reset, only release the reset line after the operating clock signal has become

stable. When switching the clock signal during program execution, wait until the target clock

signal has stabilized.

 When the clock signal is generated with an external resonator (or from an external

oscillator) during a reset, ensure that the reset line is only released after full stabilization of

the clock signal. Moreover, when switching to a clock signal produced with an external

resonator (or by an external oscillator) while program execution is in progress, wait until

the target clock signal is stable.

5. Differences between Products

Before changing from one product to another, i.e. to one with a different part number, confirm

that the change will not lead to problems.

 The characteristics of MPU/MCU in the same group but having different part numbers may

differ because of the differences in internal memory capacity and layout pattern. When

changing to products of different part numbers, implement a system-evaluation test for

each of the products.

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