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System Integration Unit (SIU)
MPC5644A Microcontroller Reference Manual, Rev. 6
402
Freescale Semiconductor
The following sections describe PCR functions using maps that show the fields contained in each register.
Refer to
for the details of each field.
shows a sample PCR map. Please note the following:
•
The register bit numbering order follows the Power Architecture standard of the most significant
bit being bit 0. Field bit ranges are the opposite—the least significant bit is referred to as bit 0.
•
Bit 0 is an example of a reserved field. It is read-only and always returns a value of 0.
HYS
4
Input hysteresis
Controls whether hysteresis is enabled for the pad.
0 Disable hysteresis for the pad.
1 Enable hysteresis for the pad.
SRC
Slew rate control
Controls slew rate for the pad. Slew rate control pertains to pins with slow or medium I/O pad types, and
the output signals are driven according to the value of this field. Actual slew rate depends on the pad type
and load. Refer to the electrical specifications for this information.
00 Minimum slew rate
01 Medium slew rate
10 Invalid value
11 Maximum slew rate
WPE
5
Weak pullup/down enable
Controls whether the weak pullup/down devices are enabled/disabled for the pad. Pullup/down devices
are enabled by default.
0 Disable weak pull device for the pad.
1 Enable weak pull device for the pad.
WPS
Weak pullup/down select
Controls whether weak pullup or weak pulldown devices are used for the pad when weak pullup/down
devices are enabled.
The WKPCFG pin determines whether pullup or pulldown devices are enabled during reset. The WPS
bit determines whether weak pullup or pulldown devices are used after reset, or for pads in which the
WKPCFG pin does not determine the reset weak pullup/down state.
0 Pulldown is enabled for the pad.
1 Pullup is enabled for the pad.
1
In cases where an I/O function is either input-only or output-only the IBE and OBE bits do not need to be set to enable
pin I/O.
2
For I/O functions that change direction dynamically, such as the external data bus, switching between input and output is
handled internally and the IBE and OBE bits are ignored.
3
If a pin is configured as an input, the ODE, SRC, and DSC bits do not apply.
4
If a pin is configured as an output, the HYS bit does not apply.
5
When a pin is configured as an output, the weak internal pull up/down is disabled regardless of the WPE or WPS settings
in the PCR.
Table 16-18. SIU_PCR field description (continued)
Field
Description
Summary of Contents for MPC5644A
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