Table of Contents
Advertisement
APPENDIX
6.3 Notes on use
6.3.10 Note on multi-master I
This function is used at f(X
6.3.11 Termination of unused pins
(1) Proper termination of unused pins
Output ports : Open
Input ports :
Connect each pin to V
Ports that permit the selecting of a built-in pull-up or pull-down resistor can also use this resistor.
As for pins whose potential affects to operation modes such as pins CNV
the V
pin or the V
CC
I/O ports :
•Set the I/O ports for the input mode and connect them to V
1 kΩ to 10 kΩ. Set the I/O ports for the output mode and open them at "L" or "H."
•When opening them in the output mode, the input mode of the initial status remains until the mode
of the ports is switched over to the output mode by the program after reset. Thus, the potential
at these pins is undefined and the power source current may increase in the input mode. With
regard to an effects on the system, thoroughly perform system evaluation on the user side.
•Since the direction register setup may be changed because of a program runaway or noise, set
direction registers by program periodically to increase the reliability.
(2) Incorrect termination of unused pins
input ports and I/O ports :
Do not open in the input mode.
Reason
•The power supply current may increase depending on the first-stage circuit.
•An effect due to noise may be easily produced as compared with proper termination (1).
shown on the above.
I/O ports :
Set for input mode and do not connect to V
Reason
If the direction register setup changes for the output mode because of a program runaway or
noise, a short circuit may occur between a port and V
I/O ports :
Set for the input mode and do not connect multiple ports in a lump to V
Reason
If the direction register setup changes for the output mode because of a program runaway or
noise, a short circuit may occur between ports.
(3) At the termination of unused pins, perform wiring at the shortest possible distance (20 mm or
less) from microcomputer pins.
6-10
2
C-BUS interface
) = 8.0 MHz of oscillation frequency.
IN
or V
through each resistor of 1 kW to 10 kW.
CC
SS
pin according to their operation mode.
SS
7220 Group User's Manual
or V
CC
or V
directly.
CC
SS
(or V
).
CC
SS
, INT or others, select
SS
through each resistor of
SS
or V
through a resistor.
CC
SS
Advertisement
Table of Contents
