![](http://datasheet.mmic.net.cn/Freescale-Semiconductor/MC68F375MZP33R2_datasheet_98733/MC68F375MZP33R2_180.png)
MC68F375
QUEUED ANALOG-TO-DIGITAL CONVERTER MODULE-64
MOTOROLA
REFERENCE MANUAL
Rev. 25 June 03
5-4
5.3.1 Port A Pin Functions
The eight port A pins can be used as analog inputs, or as a bidirectional 8-bit digital
input/output port.
5.3.1.1 Port A Analog Input Pins
When used as analog inputs, the eight port A pins are referred to as AN[59:52]. Due
to the digital output drivers associated with port A, the analog characteristics of port A
are different from those of port B. All of the analog signal input pins may be used for
at least one other purpose.
5.3.1.2 Port A Digital Input/Output Pins
Port A pins are referred to as PQA when used as a bidirectional 8-bit digital input/out-
put port. These eight pins may be used for general-purpose digital input signals or
digital output signals.
Port A pins are connected to a digital input synchronizer during reads and may be used
as general purpose digital inputs. Since port A read captures the data on all pins,
including those used for digital outputs or analog inputs, the user should employ a
“masking” operation to filter the inappropriate bits from the input byte.
Each port A pin is configured as input or output by programming the port data direction
register (DDRQA). Digital input signal states are read into the PORTQA data register
when DDRQA specifies that the pins are inputs. Digital data in PORTQA is driven onto
the port A pins when the corresponding bits in DDRQA specify outputs.
5.3.2 Port B Pin Functions
The eight port B pins can be used as analog inputs, or as an 8-bit digital input only port.
Refer to the following paragraphs for more information.
5.3.2.1 Port B Analog Input Pins
When used as analog inputs, the eight port B pins are referred to as AN[51:48]/
AN[3:0]. Since port B functions as analog and digital input only, the analog character-
istics are different from those of port A. All of the analog signal input pins may be used
for at least one other purpose.
5.3.2.2 Port B Digital Input Pins
Port B pins are referred to as PQB[7:0] when used as an 8-bit digital input only port. In
addition to functioning as analog input pins, the port B pins are also connected to the
input of a synchronizer during reads and may be used as general-purpose digital
inputs.
Since port B pins are input only, there is no associated data direction register. Digital
input signal states are read from the PORTQB data register. Since a port B read cap-
tures the data on all pins, including those used for analog inputs, the user should
employ a “masking” operation to filter the inappropriate bits from the input byte.
F
re
e
sc
a
le
S
e
m
ic
o
n
d
u
c
to
r,
I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
n
c
..
.