MC68HC708AS48 FREESCALE [Freescale Semiconductor, Inc], MC68HC708AS48 Datasheet - Page 191

• Manufacturer Part Number: MC68HC708AS48
• Description: Advance Information
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

15.4 Port B
15.4.1 Port B Data Register
MC68HC708AS48
MOTOROLA
—
Rev. 4.0
Functions:
Alternate
Address:
Port B is an 8-bit special function port that shares all of its pins with the
analog-to-digital converter (ADC).
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
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.
PTB7/ATD7–PTB0/ATD0 are eight of the analog-to-digital converter
channels. The ADC channel select bits, CH[4:0], determine whether
the PTB7/ATD7–PTB0/ATD0 pins are ADC channels or
general-purpose I/O pins. If an ADC channel is selected and a read of
this corresponding bit in the port B data register occurs, the data will
be 0 if the data direction for this bit is programmed as an input.
Otherwise, the data will reflect the value in the data latch. (See
Section 19. Analog-to-Digital Converter
register B (DDRB) does not affect the data direction of port B pins that
are being used by the ADC. However, the DDRB bits always
determine whether reading port B returns to the states of the latches
or logic 0.
$0001
PTB7
ATD7
Bit 7
Figure 15-5. Port B Data Register (PTB)
Input/Output (I/O) Ports
PTB6
ATD6
6
PTB5
ATD5
5
Unaffected by Reset
PTB4
ATD4
4
PTB3
ATD3
3
(ADC).) Data direction
PTB2
ATD2
2
Input/Output (I/O) Ports
Advance Information
PTB1
ATD1
1
PTB0
ATD0
Bit 0
Port B
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