
INPUT/OUTPUT PINS
7905 Group User’s Manual Rev.1.0
5-7
Fig. 5.2.6 Port peripheral circuits (3)
5.2.3 Pin P4OUTCUT/INT0 (Port-P4-output-cutoff signal input pin)
Any of bits 0 through 7 of the port P4 direction register (address C16) are forcibly cleared to “0” by input
of a falling edge to pin P4OUTCUT/INT0, regardless of the mode of port pins P40 through P47; therefore, port
pins P40 through P47 enter the input mode. After that, if it is necessary to output data from port pins P40
through P47, be sure to do as follows:
Return the input level at pin P4OUTCUT/INT0 to “H” level.
Write data to the port P4 register (address A16)’s bits, corresponding to the port P4 pins which will output
data.
Set the port P4 direction register’s bits, corresponding to the port P4 pins in , to “1” in order to set
these port pins to the output mode.
When input level at pin P4OUTCUT/INT0 is “L”, no bit of the port P4 direction register can be set to “1.”
When using port pins P40 through P47 as output port pins at all the time, connect pin P4OUTCUT/INT0 to
Vcc via a resistor. Pin P4OUTCUT/INT0 cannot serve as pin INT0.
Also, when using pin P4OUTCUT/INT0 as an input pin of an external interrupt (pin INT0), use port pins P40
through P47 in the input mode.
5.2.4 Pin P6OUTCUT/INT4 (Port-P6-output-cutoff signal input pin)
Any of bits 0 through 7 of the port P6 direction register (address 1016) are forcibly cleared to “0” by input
of a falling edge to pin P6OUTCUT/INT4, regardless of the mode of port pins P60 through P67; therefore, port
pins P60 through P67 enter the input mode. After that, if it is necessary to output data from port pins P60
through P67, be sure to do as follows:
Return the input level at pin P6OUTCUT/INT4 to “H” level.
Write data to the port P6 register (address E16)’s bits, corresponding to the port P6 pins which will output
data.
Set the port P6 direction register’s bits, corresponding to the port P6 pins in , to “1” in order to set
these port pins to the output mode.
When input level at pin P6OUTCUT/INT4 is “L”, no bit of the port P6 direction register can be set to “1.”
When using port pins P60 through P67 as output port pins at all the time, connect pin P6OUTCUT/INT4 to
Vcc via a resistor. Pin P6OUTCUT/INT4 cannot serve as pin INT4.
Also, when using pin P6OUTCUT/INT4 as an input pin of an external interrupt (pin INT4), use port pins P60
through P67 in the input mode.
P83/AN11/TXD2
P8 2/AN10/RXD0
1
P4OUTCUT/INT0, P6OUTCUT/INT4
Data bus
Direction register
Port latch
Analog input
Data bus
Port latch
Direction register
Output (internal peripheral device)
Analog input
5.2 Programmable I/O ports