Renesas J80D1 User Manual page 3

General Precautions in the Handling of Microprocessing Unit and Microcontroller Unit Products
The following usage notes are applicable to all Microprocessing 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. 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 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 a product with a different part number,
confirm that the change will not lead to problems.
⎯ The characteristics of Microprocessing unit or Microcontroller unit products in the same
group but having a different part number may differ in terms of the 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.