
INPUT/OUTPUT PORTS
4-7
RESET:
$00 (all general purpose I/O configured for input only).
0 – Bits set to zero configure the corresponding I/O pins as inputs.
1 – Bits set to one configure the corresponding I/O pins as outputs.
Bit 5 of Port D is dedicated as the active low slave select (SS) input, when the SPI system is enabled.
In SPI slave mode, DDRD bit 5 has no meaning or effect. In SPI master mode, DDRD bit 5
determines whether Port D bit 5 is an error detect input to the SPI (DDRD bit clear) or a general
purpose output line (DDRD bit set).
For bits 2, 3, & 4 (MISO, MOSI, & SCK): if the SPI is enabled and expects the bit to be an input, it
will be an input regardless of the state of the DDRD bit; if the SPI is enabled and expects the bit to
be an output, it will be an output only if the DDRD bit is set.
4.8
PORT E
Port E is an 8-bit port which supports the 8-channel A/D converter. Any channels not used
for A/D may be used as general purpose inputs.
Since there is no output drive logic associated with Port E there is no DDRE register. Port E pins
are capable of withstanding negative 1 volt transients (current limited by an external 10 k
or greater
resistor) without affecting MCU operation, other than possible loss of the A/D input sample for a
conversion being performed at the time of the transient. Using Port E pins as A/D inputs does not
affect the ability to read these pins as static inputs. However, reading Port E during an A/D
conversion sequence may inject noise into the analog input signals and may result in reduced
accuracy of the A/D result. Note that performing a digital read of Port E, with levels other than VDD
or VSS on the Port E pins, will result in greater power dissipation during the read cycle.
4.8.1
Data Register (PORTE)
PE7
PE6
PE5
PE4
PE3
PE2
PE1
PE0
PORTE
$100A
7
6
5
4
3
2
1
0
U
RESET:
Alternate Pin Function:
AN7
AN6
AN5
AN4
AN3
AN2
AN1
AN0
READ:
Any time (returns sensed levels at Port E pins).
WRITE:
Has no meaning or effect.
RESET:
Does not affect this address.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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