mc68hc908as60 Freescale Semiconductor, Inc, mc68hc908as60 Datasheet - Page 306

• Manufacturer Part Number: mc68hc908as60
• Description: Mc68hc908as60 Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Input/Output (I/O) Ports
20.4 Port B
20.4.1 Port B Data Register
Technical Data
Functions:
Address:
Alternate
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 (PTB) 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 15 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. Data
direction 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. See
Freescale Semiconductor, Inc.
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ATD7
PTB7
Bit 7
Go to: www.freescale.com
Figure 20-5. Port B Data Register (PTB)
Input/Output (I/O) Ports
ATD6
PTB6
Section 23. Analog-to-Digital Converter
6
ATD5
PTB5
5
Unaffected by reset
PTB4
ATD4
4
PTB3
ATD3
3
MC68HC908AS60 — Rev. 1.0
PTB2
ATD2
2
PTB1
ATD1
1
(ADC-15).
ATD0
PTB0
Bit 0