Input/Output (I/O) Ports (PORTS)

 

 

READ DDRA ($0004)

 

 

WRITE DDRA ($0004)

 

BUS

 

DDRAx

 

RESET

DATA

WRITE PTA ($0000)

 

INTERNAL

PTAx

 

 

 

 

READ PTA ($0000)

 

PTAx

Figure 10-4. Port A I/O Circuit

When bit DDRAx is a logic 1, reading address $0000 reads the PTAx data latch. When bit DDRAx is a logic 0, reading address $0000 reads the voltage level on the pin. The data latch can always be written, regardless of the state of its data direction bit. Table 10-1summarizes the operation of the port A pins.

Table 10-1. Port A Pin Functions

DDRA Bit

PTA Bit

I/O Pin Mode

Accesses to DDRA

Accesses to PTA

 

 

 

Read/Write

Read

Write

 

 

 

 

 

 

 

 

 

0

X(1)

Input, Hi-Z(2)

DDRA[7:0]

Pin

PTA[7:0](3)

1

X

Output

DDRA[7:0]

PTA[7:0]

PTA[7:0]

 

 

 

 

 

 

1.X = don’t care

2.Hi-Z = high impedance

3.Writing affects data register, but does not affect input.

10.3Port B

Port B is an 8-bit, general-purpose, bidirectional I/O port that shares its pins with the analog-to-digital convertor (ADC) module.

10.3.1 Port B Data Register

The port B data register (PTB) contains a data latch for each of the eight port B pins.

Address:

Read:

Write:

Reset:

$0001

 

 

 

 

 

 

 

Bit 7

6

5

4

3

2

1

Bit 0

 

 

 

 

 

 

 

 

PTB7

PTB6

PTB5

PTB4

PTB3

PTB2

PTB1

PTB0

 

 

 

 

 

 

 

 

Unaffected by reset

Figure 10-5. Port B Data Register (PTB)

PTB[7:0] — Port B Data Bits

These read/write bits are software-programmable. Data direction of each port B pin is under the control of the corresponding bit in data direction register B. Reset has no effect on port B data.

MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1

104

Freescale Semiconductor

Page 104
Image 104
Freescale Semiconductor MC68HC908MR32 manual Port B Data Register, Port a Pin Functions, Input/Output I/O Ports Ports

MC68HC908MR16, MC68HC908MR32 specifications

Freescale Semiconductor's MC68HC908MR32 and MC68HC908MR16 microcontrollers are part of the popular HC08 family, designed primarily for embedded applications. These microcontrollers are particularly favored in automotive, industrial, and consumer product sectors due to their reliability and versatility.

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The MC68HC908MR32 variant is equipped with 32KB of flash memory, which allows for the storage of complex programs and extensive data handling. In contrast, the MC68HC908MR16 features 16KB of flash memory, making it ideal for simpler applications. Both microcontrollers also come with 1KB of RAM, enabling efficient data processing and real-time operations.

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