7905 datasheet(80/565 Pages) RENESAS

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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:

➀ Return the input level at pin P4OUTCUT/INT0 to “H” level.

➁ Write data to the port P4 register (address A16)’s bits, corresponding to the port P4 pins which will output

data.

➂ Set the port P4 direction register’s bits, corresponding to the port P4 pins in ➁, 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:

➀ Return the input level at pin P6OUTCUT/INT4 to “H” level.

➁ Write data to the port P6 register (address E16)’s bits, corresponding to the port P6 pins which will output

data.

➂ Set the port P6 direction register’s bits, corresponding to the port P6 pins in ➁, 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

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

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