HC705JB2GRSSLASHH datasheet(50/128 Pages) NXP

50 / 128 page

GENERAL RELEASE SPECIFICATION

August 28, 1998

INPUT/OUTPUT PORTS

MC68HC705JB2

7-4

REV 1.1

7.2

PORT B

Port B is a 3-bit bidirectional port which functions as shown in Figure 7-2. Each

Port B pin is controlled by the corresponding bits in a data direction register, a

data register, and a pulldown/up register. The Port B Data Register is located at

address $0001. The Port B Data Direction Register (DDRB) is located at address

$0005. The Port B Pulldown/up Register (PDURB) is located at address $0011.

Reset clears the DDRB and the PDURB. The Port B Data Register is unaffected

by reset.

PB0 is a standard push-pull I/O pin with pulldown option; and is shared with TCAP.

PB1 and PB2 are of open-drain type, with pullup option, each capable of sinking

25mA (typical) current at VOL 0.5V max. These two pins may be connected

together to constitute a single pin capable of sinking 50mA (typical). In this case,

both PB1 and PB2 data bits will have to be written with the same value at the

same write cycle.

Figure 7-2. Port B I/O Circuitry

7.2.1 Port B Data Register

All Port B I/O pins have a corresponding bit in the Port B Data Register. When a

Port B pin is programmed as an output the state of the corresponding data

programmed as an input, any read of the Port B Data Register will return the logic

state of the corresponding I/O pin. The Port B data register is unaffected by reset.

Unused bits will always read as logic zeros, and any write to these bits will be

ignored. The Port B data register is unaffected by reset.

Write $0011

Read $0001

Write $0001

Read $0005

Write $0005

Internal HC05

Data Bus

100

µA

Pulldown

Data

Output

Mask Option

(Software Pulldown/up Inhibit)

Reset

(RST)

Data Direction

Pulldown/up

VDD

100K

Pullup

Note: Each I/O port pin can have either pullup or pulldown device, but not both.

PB1 and PB2 output drivers are of open-drain type

I/O Pin

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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