MPC555CME Freescale Semiconductor, MPC555CME Datasheet - Page 420

• Manufacturer Part Number: MPC555CME
• Description: KIT EVALUATION FOR MPC555
• Manufacturer: Freescale Semiconductor
• Type: Microcontrollerr

Specifications of MPC555CME

• Contents: Module Board, Installation Guide, Power Supply, Cable, Software and more
• Processor To Be Evaluated: MPC555
• Data Bus Width: 32 bit
• Interface Type: RS-232
• For Use With/related Products: MPC555
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

13.6.1 Port Data Register
13.6.2 Port Data Direction Register
MPC555
USER’S MANUAL
current effect of mid-level signals on the inputs used for analog signals. Digital input
signals must meet the input low voltage (VIL) or input high voltage (VIH) specifications.
If an analog input pin does not meet the digital input pin specifications when a digital
port read operation occurs, an indeterminate state is read. To avoid reading inappro-
priate values on analog inputs, the user software should employ a “masking” opera-
tion.
During a port data register read, the actual value of the pin is reported when its corre-
sponding bit in the data direction register defines the pin to be an input (port A only).
When the data direction bit specifies the pin to be an output, the content of the port
data register is read. By reading the latch which drives the output pin, software instruc-
tions that read data, modify it, and write the result, like bit manipulation instructions,
work correctly.
There is one special case to consider for digital I/O port operation. When the MUX (ex-
ternally multiplexed) bit is set in QACR0, the data direction register settings are ig-
nored for the bits corresponding to PQA[2:0], the three multiplexed address MA[2:0]
output pins. The MA[2:0] pins are forced to be digital outputs, regardless of the data
direction setting, and the multiplexed address outputs are driven. The data returned
during a port data register read is the value of the multiplexed address latches which
drive MA[2:0], regardless of the data direction setting.
QADC64 ports A and B are accessed through two 8-bit port data registers (PORTQA
and PORTQB). Port A pins 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 ad-
dress outputs MA[2:0].
Port B pins are referred to as PQB when used as an 8-bit input-only digital port. Port
B can also be used for non-multiplexed AN[51:48]/AN[3:0] and multiplexed ANz, ANy,
ANx, ANw analog inputs.
PORTQA and PORTQB are unaffected by reset. Refer to
ister
The port data direction register (DDRQA) is associated with the port A digital I/O pins.
These bi-directional pins may have somewhat higher leakage and capacitance speci-
fications.
Any bit in this register set to one configures the corresponding pin as an output. Any
bit in this register cleared to zero configures the corresponding pin as an input. Soft-
ware is responsible for ensuring that DDRQA bits are not set to one on pins used for
analog inputs. When a DDRQA bit is set to one and the pin is selected for analog con-
version, the voltage sampled is that of the output digital driver as influenced by the
load.
/
for register and bit descriptions.
MPC556 QUEUED ANALOG-TO-DIGITAL CONVERTER MODULE-64
Rev. 15 October 2000
NOTE
13.12.4 Port A/B Data Reg-
MOTOROLA
13-8