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MCF51QE128 MCU Series Reference Manual, Rev. 3
Freescale Semiconductor 127
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Chapter 6 Parallel Input/Output Control
6.7.4.2 Port D Data Direction Register (PTDDD)
6.7.4.3 Port D Pull Enable Register (PTDPE)
The port D pull enable register enables pull-ups on the corresponding PTD pin. In some cases, a pull-down
device is enabled if pull-downs are supported by an alternate pin function (e.g., KBI).
Table 6-19. PTDD Register Field Descriptions
Field Description
7–0
PTDDn
Port D Data Register Bits. For port D pins configured as inputs, reads return the logic level on the pin. For port
D pins configured as outputs, reads return the last value written to this register.
Writes are latched into all bits of this register. For port D pins configured as outputs, the logic level is driven out
the corresponding MCU pin.
Reset forces PTDD to all 0s, but these 0s are not driven out the corresponding pins because reset also configures
all port pins as high-impedance inputs with pull-ups/pull-downs disabled.
76543210
R
PTDDD7 PTDDD6 PTDDD5 PTDDD4 PTDDD3 PTDDD2 PTDDD1 PTDDD0
W
Reset:00000000
Figure 6-23. Port D Data Direction Register (PTDDD)
Table 6-20. PTDDD Register Field Descriptions
Field Description
7–0
PTDDDn
Data Direction for Port D Bits. These read/write bits control the direction of port D pins and what is read for PTDD
reads.
0 Input (output driver disabled) and reads return the pin value.
1 Output driver enabled for port D bit n and PTDD reads return the contents of PTDDn.
76543210
R
PTDPE7 PTDPE6 PTDPE5 PTDPE4 PTDPE3 PTDPE2 PTDPE1 PTDPE0
W
Reset:00000000
Figure 6-24. Internal Pull Enable for Port D Register (PTDPE)
Table 6-21. PTDPE Register Field Descriptions
Field Description
7–0
PTDPEn
Internal Pull Enable for Port D Bits. Each of these control bits determines if the internal pull-up or pull-down device
is enabled for the associated PTD pin. For port D pins configured as outputs, these bits have no effect and the
internal pull devices are disabled.
0 Internal pull-up/pull-down device disabled for port D bit n.
1 Internal pull-up/pull-down device enabled for port D bit n.