General Precautions in the Handling of Micro processing Unit and Microcontroller
Unit Products
The following usage notes are applicable to all Micro processing unit and Microcontroller unit products from Renesas. For detailed usage notes on the products covered by
this document, refer to the relevant sections of the document as well as any technical updates that have been issued for the products.
1. Precaution against Electrostatic Discharge (ESD)
A strong electrical field, when exposed to a CMOS device, can cause destruction of the gate oxide and ultimately degrade the device operation. Steps must be taken to
stop the generation of static electricity as much as possible, and quickly dissipate it when it occurs. Environmental control must be adequate. When it is dry, a
humidifier should be used. This is recommended to avoid using insulators that can easily build up static electricity. Semiconductor devices must be stored and
transported in an anti-static container, static shielding bag or conductive material. All test and measurement tools including work benches and floors must be
grounded. The operator must also be grounded using a wrist strap. Semiconductor devices must not be touched with bare hands. Similar precautions must be taken for
printed circuit boards with mounted semiconductor devices.
2. Processing at power-on
The state of the product is undefined at the time 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 time 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 time 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 time when power is supplied until the power reaches the level at which resetting is specified.
3. Input of signal during power-off state
Do not input signals or an I/O pull-up power supply while the device is powered off. The current injection that results from input of such a signal or I/O pull-up power
supply may cause malfunction and the abnormal current that passes in the device at this time may cause degradation of internal elements. Follow the guideline for
input signal during power-off state as described in your product documentation.
4. Handling of unused pins
Handle unused pins in accordance 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 near the 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.
5. Clock signals
After applying a reset, only release the reset line after the operating clock signal becomes stable. When switching the clock signal during program execution, wait
until the target clock signal is 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. Additionally, 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.
6. Voltage application waveform at input pin
Waveform distortion due to input noise or a reflected wave may cause malfunction. If the input of the CMOS device stays in the area between V
IL
(Max.) and V
IH
(Min.) due to noise, for example, the device may malfunction. Take care to prevent chattering noise from entering the device when the input level is fixed, and also in
the transition period when the input level passes through the area between V
IL
(Max.) and V
IH
(Min.).
7. Prohibition of access to reserved addresses
Access to reserved addresses is prohibited. The reserved addresses are provided for possible future expansion of functions. Do not access these addresses as the
correct operation of the LSI is not guaranteed.
8. Differences between products
Before changing from one product to another, for example to a product with a different part number, confirm that the change will not lead to problems. The
characteristics of a micro processing unit or microcontroller unit products in the same group but having a different part number might differ in terms of internal
memory capacity, layout pattern, and other factors, which can affect the ranges of electrical characteristics, such as characteristic values, operating margins, immunity
to noise, and amount of radiated noise. When changing to a product with a different part number, implement a system-evaluation test for the given product.
