68HC705JB4 datasheet(49/134 Pages) FREESCALE

49 / 134 page

February 24, 1999

GENERAL RELEASE SPECIFICATION

MC68HC05JB4

INPUT/OUTPUT PORTS

MOTOROLA

REV 2

7-3

7.2.2 Port-A Data Direction Register

7.2.3 Port-A Pull-up Control Register

7.3

PORT-B

Port-B is a 5-bit bi-directional port. The port-B data register is at $0001 and the

data direction register (DDRB) is at $0005. Reset does not affect the data regis-

ters, but clears the data direction registers, thereby returning the port pins to

inputs. Writing a ‘one’ to a DDR bit sets the corresponding port bit to output mode.

Each pin in Port-B has an internal pull-up resistor (50k

Ω typical) which can be

individually enabled by writing a ‘1’ to the corresponding bit in the Port-B pull-up

control register at location $0011.

All Port-B pins have built in Slow Output edge transition driver which can be

enabled by writing a ‘1’ to bit-6 of Port-B data direction register at location $0005.

When PB0 is conﬁgured as an input, it also serves as the input capture pin for the

16-bit Timer. When conﬁgured as output, the input to the input capture will be per-

manently tied “low” and no input capture can be generated. PB0 has built-in

schmitt triggered input to improve noise immunity.

PB3 and PB4 also serve as extra ADC inputs, AD4 and AD5. When a port pin is

selected as ADC input and the ADON bit is set to ‘1’, the pin will be conﬁgured as

input pin and its pull-up will be disabled automatically regardless of the status of

the DDR-bit. The value of the DDR-bit will not be affected.

If the pull-up device is enabled and the port pin is conﬁgured as output, the output

port becomes an open-drain output with 50k

Ω pull-up.

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

DDRA

DDRA7

DDRA6

DDRA5

DDRA4

DDRA3

DDRA2

DDRA1

DDRA0

$0004

reset:

00000000

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

PURA

$0010

PURA7

PURA6

PURA5

PURA4

PURA3

PURA2

PURA1

PURA0

reset:

00000000

Port-B PURX

Port-B DDRX

Pin Configuration

Input

Output Push/Pull

Input with 50k pull-up

Open-drain Output with 50k pull-up

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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