FXTH870xD
Sensors
46
Freescale Semiconductor, Inc.
An internal pullup device can be enabled for each port pin by setting the corresponding bit in one of the pullup enable registers
(PTxPEn). The pullup device is disabled if the pin is configured as an output by the general purpose I/O control logic or any shared
peripheral function regardless of the state of the corresponding pullup enable register bit. The pullup device is also disabled if the
pin is controlled by an analog function.
6.1
Unused Pin Configuration
Any general purpose I/O pins which are not used in the application must be properly configured to avoid a floating input that could
cause excessive supply current, I
DD
.
When the device comes out of the reset state the Freescale supplied firmware will not configure any of the general purpose I/O
pins.
Recommended configuration methods are:
1.
Configure the general purpose I/O pin as an input (PTxDDn = 0) with the pin connected to the V
DD
source
;
use a
pullup resistor of 10-51 k
to assure sufficient noise immunity.
2.
Configure the general purpose I/O pin as an input (PTxDDn = 0) with the internal pullup activated (PTxPEn = 1) and
leave the pin disconnected.
3.
Configure the general purpose I/O pin as an output (PTxDDn = 1) and drive the pin low (PTxDn = 0) and leave the pin
disconnected.
In cases where GPIOs are directly connected to AV
DD
, V
DD
, AV
SS
, V
SS
or RV
SS
,
user application should configure the GPIO as
an input with the internal pull-up disabled, in order to prevent software code faults from causing excessive supply current states
should these pins become outputs.
6.2
Pin Behavior in STOP Modes
Pin behavior following execution of a STOP instruction depends on the STOP mode that is entered. An explanation of pin
behavior for the various STOP modes follows:
•
In STOP1 mode, all internal registers including general purpose I/O control and data registers are powered off. Each of the
pins assumes its default reset state (input buffer, output buffer and internal pullup disabled). Upon exit from STOP1, all pins
must be reconfigured the same as if the MCU had been reset.
•
In STOP4 mode, all pin states are maintained because internal logic stays powered up. Upon recovery, all pin functions are
the same as before entering STOP4.
6.3
General Purpose I/O Registers
This section provides information about the registers associated with the general purpose I/O ports and pin control functions.
These general purpose I/O registers are located in page zero of the memory map and the pin control registers are located in the
high page register section of memory.
6.4
Port A Registers
Port A general purpose I/O function is controlled by the registers described in this section.
$0000
Bit 7
6
5
4
3
2
1
Bit 0
R
PTAD[4:0]
W
Reset:
0
0
0
0
0
0
0
0
= Reserved
Figure 30. Port A Data Register (PTAD)
Содержание FXTH870 D Series
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