MC908AZ60ACFUER Datasheet, PDF (252/414 Pages) Freescale Semiconductor, Inc – To provide the most up-to-date information, the revision of our documents on the World Wide Web will be the most current. Your printed copy may be an earlier revision. To verify you have the latest information available, refer to:

Input/Output Ports
22.3 Port B
Port B is an 8-bit special function port that shares all of its pins with the analog-to-digital converter.
22.3.1 Port B Data Register
The port B data register contains a data latch for each of the eight port B pins.
Address:
Read:
Write:
Reset:
Alternative
Functions:
$0001
Bit 7
PTB7
ATD7
6
5
4
3
2
PTB6
PTB5
PTB4
PTB3
PTB2
Unaffected by Reset
ATD6
ATD5
ATD4
ATD3
ATD2
Figure 22-5. Port B Data Register (PTB)
1
PTB1
ATD1
Bit 0
PTB0
ATD0
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.
ATD[7:0] — ADC Channels
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 Chapter 26 Analog-to-Digital Converter
(ADC)). 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 0.
MC68HC908AZ60A • MC68HC908AS60A • MC68HC908AS60E Data Sheet, Rev. 6
252
Freescale Semiconductor