MC68HC705P9CS datasheet(86/160 Pages) FREESCALE

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Parallel Input/Output (I/O) Ports

Technical Data

MC68HC705P9 — Rev. 4.0

Parallel Input/Output (I/O) Ports

MOTOROLA

SDI — Serial Data Input

When the SIOP is enabled, SDI is the SIOP data input.

SDO — Serial Data Output

When the SIOP is enabled, SDO is the SIOP data output.

7.4.2 Data Direction Register B (DDRB)

Data direction register B determines whether each port B pin is an input

or an output.

NOTE:

Enabling and then disabling the SIOP configures data direction register

B for SIOP operation and can also change the port B data register. After

disabling the SIOP, initialize data direction register B and the port B data

DDRB[7:5] — Data Direction Register B Bits

These read/write bits control port B data direction. Reset clears

DDRB[7:5], configuring all three port B pins as inputs.

1 = Corresponding port B pin configured as output

0 = Corresponding port B pin configured as input

NOTE:

Avoid glitches on port B pins by writing to the port B data register before

changing data direction register B bits from 0 to 1.

Figure 7-7 shows the I/O logic of port B.

$0005

Bit 7

54321

Bit 0

Read:

DDRB7

DDRB6

DDRB5

00000

Write:

Reset:

000000

= Unimplemented

Figure 7-6. Data Direction Register B (DDRB)

Freescale Semiconductor, Inc.

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