7540 datasheet(36/366 Pages) RENESAS

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1-17

REJ09B0018-0200Z

Rev.2.00

Jun 21, 2004

7540 Group

HARDWARE

FUNCTIONAL DESCRIPTION

I/O Ports

[Direction registers] PiD

The I/O ports have direction registers which determine the input/

output direction of each pin. Each bit in a direction register corre-

sponds to one pin, and each pin can be set to be input or output.

When “1” is set to the bit corresponding to a pin, this pin becomes

an output port. When “0” is set to the bit, the pin becomes an in-

put port.

When data is read from a pin set to output, not the value of the pin

itself but the value of port latch is read. Pins set to input are float-

ing, and permit reading pin values.

If a pin set to input is written to, only the port latch is written to and

the pin remains floating.

[Pull-up control register] PULL

By setting the pull-up control register (address 001616), ports P0

and P3 can exert pull-up control by program. However, pins set to

output are disconnected from this control and cannot exert pull-up

control.

Note: P26/AN6, P27/AN7, P35 and P36 do not exist for the 32-pin

version.

Accordingly, the following settings are required;

• Set direction registers of ports P26 and P27 to output.

• Set direction registers of ports P35 and P36 to output.

[Port P1P3 control register] P1P3C

By setting the port P1P3 control register (address 001716), a

CMOS input level or a TTL input level can be selected for ports

P10, P12, P13, P36, and P37 by program.

Fig. 16 Structure of port P1P3 control register

Fig. 15 Structure of pull-up control register

Port P1P3 control register

(P1P3C: address 0017 16, initial value: 00 16)

P37/INT0 input level selection bit

0 : CMOS level

1 : TTL level

P36/INT1 input level selection bit

0 : CMOS level

1 : TTL level

P10,P12,P13 input level selection bit

0 : CMOS level

1 : TTL level

Not used

Note: Keep setting the P3 6/INT1 input level selection bit

to “0” (initial value) for 32-pin version.

Pull-up control register

(PULL: address 001616, initial value: 0016)

P00 pull-up control bit

0 : Pull-up Off

1 : Pull-up On

P37 pull-up control bit

P35, P36 pull-up control bit

P34 pull-up control bit

P30 – P33 pull-up control bit

P04 – P07 pull-up control bit

P02, P03 pull-up control bit

P01 pull-up control bit

Note: Pins set to output ports are disconnected from pull-up control.

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