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Programming the QADC64E Registers
14.3.3
Port Data Register
QADC64E port A is accessed through two 8-bit port data registers, PORTQA and
PORTQB.
Port A signals are referred to as PQA[7:0] when used as 8-bit general-purpose digital input
or output signals. It is configured as a digital input or digital output using the data direction
register, DDRQA. When Port A is configured as an input, a read of the PORTQA register
returns the actual PQA[7:0] signal values. When Port A is configured as an output, the
contents of port register PQA are driven on the port A signals. Port A can also be used as
analog inputs AN[59:52] and external multiplexer address outputs MA[2:0].
During a port data register read, the actual value of the signal is reported when its
corresponding bit in the data direction register defines the signal to be an input. When the
data direction bit specifies the signal to be an output, the content of the port data register is
read.
PORTQA is not initialized by reset.
.
MSB
1
0
Field PQA7 PQA6 PQA5 PQA4 PQA3 PQA2 PQA1 PQA0
SRESET
Addr
Bits
Name
0:7
PQA[7:0] Port A signals are referred to as PQA when used as an 8-bit input/output port. Port A can also be
used for analog inputs (AN[59:52]), and external multiplexer address outputs (MA[2:0]).
8:15
—
Reserved.
14.3.4
Port Data Direction Register
The port data direction register (DDRQA) are associated with the Port A digital I/O signals.
Refer to Appendix E, "Electrical Characteristics" for more information. Any bit set to one
in this register configures the corresponding signal as an output. Any bit cleared to zero in
this register configures the corresponding signal as an input. The software is responsible for
ensuring that DDR bits are not set to one on signals used for analog inputs. When the DDR
bit is set to one and the signal is selected for analog conversion, the voltage sampled is that
of the output digital driver as influenced by the load.
14-14
2
3
4
5
0x30 4806 (PORTQA_A); 0x30 4807 (PORTQB_A)
Figure 14-7. Port A Data Register (PORTQA)
Table 14-6. PORTQA Bit Descriptions
MPC533 Reference Manual
PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE
6
7
8
9
Undefined
Description
10
11
12
13
—
MOTOROLA
14
LSB
15
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