MC68HC908AB32 MOTOROLA [Motorola, Inc], MC68HC908AB32 Datasheet - Page 318

• Manufacturer Part Number: MC68HC908AB32
• Description: HCMOS Microcontroller Unit
• Manufacturer: MOTOROLA [Motorola, Inc]

Input/Output (I/O) Ports
17.4 Port B
17.4.1 Port B Data Register (PTB)
Technical Data
318
NOTE:
Alternative Function:
Address:
Port B is an 8-bit special function port that shares all eight of its port pins
with the analog-to-digital converter (ADC) module (see
Analog-to-Digital Converter
The port B data register contains a data latch for each of the eight port B
pins.
PTB[7:0] — Port B Data Bits
ATD[7:0] — ADC channels
Care must be taken when reading port B while applying analog voltages
to ATD[7:0] pins. If the appropriate ADC channel is not enabled,
excessive current drain may occur if analog voltages are applied to the
PTBx/ATDx pin, while PTB is read as a digital input. Those ports not
selected as analog input channels are considered digital I/O ports.
Reset:
Read:
Write:
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.
ATD[7:0] are pins used for the input channels to the analog-to-digital
converter module. The channel select bits in the ADC status and
control register define which port B pin will be used as an ADC input
and overrides any control from the port I/O logic by forcing that pin as
the input to the analog circuitry.
Freescale Semiconductor, Inc.
For More Information On This Product,
$0001
PTB7
ATD7
Bit 7
Figure 17-5. Port B Data Register (PTB)
Go to: www.freescale.com
Input/Output (I/O) Ports
PTB6
ATD6
6
PTB5
ATD5
5
(ADC)).
Unaffected by reset
PTB4
ATD4
4
PTB3
ATD3
3
MC68HC908AB32
PTB2
ATD2
2
Section 14.
PTB1
ATD2
1
MOTOROLA
—
Rev. 1.0
PTB0
ATD0
Bit 0