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 may occur due to the false recognition of the pin state as an input signal.
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 type number,
confirm that the change will not lead to problems.
⎯ The characteristics of MPU/MCU in the same group but having different type numbers
may differ because of the differences in internal memory capacity and layout pattern.
When changing to products of different type numbers, implement a system-evaluation
test for each of the products.
Rev.4.00 Mar. 27, 2008, Page iii of xliv
REJ09B0108-0400
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