7549 datasheet(15/84 Pages) RENESAS

15 / 84 page

Rev.2.01

Oct 15, 2007

Page 15 of 81

REJ03B0202-0201

7549 Group

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

corresponds 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 input 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

floating, 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.

If the port P20 is used as output port, write “1” to the port P20

direction register after reset.

[Port P0 drive capacity control register] DCCR

By setting the Port P0 drive capacity control register (address

000C16), the drive capacity of the N-channel output transistor for

the port P0 can be selected.

[Pull-up control registers] PULL0, PULL1

By setting the pull-up control registers (address 000D16 and

000E16), ports P0 and P1 can exert pull-up control by program.

However, this is valid only when the port direction registers are

set to input.

When they are set to output, setting “pull-up on” does not pull up

the ports.

Fig 13. Structure of port P0 drive capacity control

Fig 14. Structure of port P0 pull-up control register

Fig 15. Structure of port P1 control register

Port P00 drive capacity selection bit

Port P01 drive capacity selection bit

Port P02 drive capacity selection bit

Port P03 drive capacity selection bit

Port P04 drive capacity selection bit

Port P05 drive capacity selection bit

Port P06 drive capacity selection bit

Port P07 drive capacity selection bit

0: weakness

1: strength

Port P0 drive capacity control register

(DCCR: address 000C16, initial value: 0016)

P00 pull-up control bit

P01 pull-up control bit

P02 pull-up control bit

P03 pull-up control bit

P04 pull-up control bit

P05 pull-up control bit

P06 pull-up control bit

P07 pull-up control bit

0: Pull-up is disabled

1: Pull-up is enabled

Port P0 pull-up control register

(PULL0: address 000D16, initial value: 0016)

P10 pull-up control bit

P11 pull-up control bit

P12 pull-up control bit

P13 pull-up control bit

P14 pull-up control bit

P15 pull-up control bit

P16 pull-up control bit

P17 pull-up control bit

0: Pull-up is disabled

1: Pull-up is enabled

Port P1 pull-up control register

(PULL1: address 000E16, initial value: 0016)

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