UPD784026 Renesas Electronics Corporation., UPD784026 Datasheet - Page 677

• Manufacturer Part Number: UPD784026
• Description: 16/8-bit Single-chip Microcontrollers
• Manufacturer: Renesas Electronics Corporation.

(2) Is the input pin level appropriate?
(3) Are pull-up resistors necessary?
(4) Is processing of the address bus, address/data bus, etc., appropriate?
The voltage level input to each pin should be in the range between V
this range is applied, the current consumption will increase and the reliability of the PD784026 may be adversely
affected.
Also ensure that an intermediate potential is not applied.
An unnecessary pull-up resistor will increase the current consumption and cause a latchup of other devices. A mode
should be specified in which pull-up resistors are used only for parts that require them.
If there is a mixture of parts that do and do not require pull-up resistors, for parts that do, you should connect a pull-
up resistor externally and specify a mode in which the internal pull-up resistor is not used.
In STOP mode and IDLE mode, the address bus, address/data bus, RD and WR pins become high-impedance.
Normally, these pins are pulled high with a pull-up resistor. If this pull-up resistor is connected to the backed-up power
supply, then if the input impedance of circuitry connected to the non-backed-up power supply is low, a current will flow
through the pull-up resistor, and the current consumption will increase. Therefore, the pull-up resistor should be
connected to the non-backed-up power supply side as shown in Figure 22-10.
Also, in STOP mode and IDLE mode the ASTB pin also becomes high impedance, and the REFRQ/HLDAK pin adopts
a fixed level. Countermeasures should be taken with reference to the points noted in (1).
The voltage level input to the WAIT/HLDRQ pin should be in the range between V
a voltage outside this range is applied, the current consumption will increase and the reliability of the PD784026 may
be adversely affected.
PD784026
(n = 0-7)
V
V
Figure 22-10 Example of Address/Data Bus Processing
DD
ADn
SS
Backed-Up Power Supply
CHAPTER 22 STANDBY FUNCTION
IN/OUT
V
CMOS IC, etc.
V
DD
SS
Non-Backed-Up Power Supply
SS
potential and V
SS
DD
potential and V
potential. If a voltage outside
DD
potential. If
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