T48C893 datasheet(24/82 Pages) ATMEL

24 / 82 page

T48C893

Rev. A4, 22-Jan-02

24 (82)

4.2.2

Bidirectional Port 2

This, and all other bidirectional ports include a bitwise

programmable Control Register (P2CR), which enables

the individual programming of each port bit as input or

output. It also opens up the possibility of reading the pin

condition when in output mode. This is a useful feature

for self testing and for serial bus applications.

Port 2 however, has an increased drive capability and an

additional low resistance pull-up/-down transistor mask

option.

Master reset

BP2y

Mask options

P2DATy

P2CRy

I/O Bus

Switched

Static

Pull-up

(Data out)

(Direction)

Static

Pull-down

pull-down

pull-up

Figure 23. Bidirectional Port 2

Port 2 Data Register (P2DAT)

Primary register address: ’2’hex

Bit 3 *

Bit 2

Bit 1

Bit 0

P2DAT

P2DAT3

P2DAT2

P2DAT1

P2DAT0

Reset value: 1111b

* Bit 3 –> MSB, Bit 0 –> LSB

Port 2 Control Register (P2CR)

Auxiliary register address: ’2’hex

Bit 3

Bit 2

Bit 1

Bit 0

P2CR

P2CR3

P2CR2

P2CR1

P2CR0

Reset value: 1111b

Value: 1111b means all pins in input mode

Code

3 2 1 0

Function

x x x 1

BP20 in input mode

x x x 0

BP20 in output mode

x x 1 x

BP21 in input mode

x x 0 x

BP21 in output mode

x 1 x x

BP22 in input mode

x 0 x x

BP22 in output mode

1 x x x

BP23 in input mode

0 x x x

BP23 in output mode

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