Parallel Input/Output Control
MCF51CN128 Reference Manual, Rev. 6
9-5
Freescale Semiconductor
NOTE
The full complement of pin controls may not be present on all Freescale
devices. See the summary table earlier in the chapter to determine which of
these are present on your device.
Refer to tables in
,” for the absolute address assignments for all registers. This section
refers to registers and control bits only by their names.
NOTE
A Freescale Semiconductor-provided equate or header file normally is used
to translate these names into the appropriate absolute addresses.
9.2.2.1
Port x Pull Enable Register (PTxPE)
An internal pull-up device can be enabled for each port pin by setting the corresponding bit in the pull-up
enable register (PT
x
PE[n]). The pull-up device is disabled if the pin is either:
•
Configured as an output by the parallel I/O control logic
•
Configured as a shared peripheral function
•
Controlled by an analog function.
•
At reset, except for RESETB and BKGD/MS.
Table 9-6. Register Set Summary
Register
Description
Access
PTxPE
Port x Pull Enable Register
read/write
PTxSE
Port x Slew Rate Enable Register
read/write
PTxDS
Port x Drive Strength Selection Register
read/write
PTxIFE
Port x Input Filter Enable Register
read/write
7
6
5
4
3
2
1
0
R
PTxPE7
PTxPE6
PTxPE5
PTxPE4
PTxPE3
PTxPE2
PTxPE1
PTxPE0
W
Reset:
0
0
0
0
0
0
0
0
Figure 9-2. Internal Pull Enable for Port x Register (PTxPE)
Table 9-7. PTxPE Field Descriptions
Field
Description
7–0
PTxPE
n
Internal Pull Enable for Port x Bits
— Each of these control bits determines if the internal pull-up device is
enabled for the associated PTx pin. For Port x pins that are configured as outputs, these bits have no effect and
the internal pull devices are disabled.
0 Internal pull-up device disabled for Port x bit
n
.
1 Internal pull-up device enabled for Port x bit
n
.