User`s guide

i.MX53 System Development User’s Guide, Rev. 1
Freescale Semiconductor 13-1
Chapter 13
Configuring the IOMUX Controller (IOMUXC)
Before using the i.MX53 pins (or pads), users must select the desired function and correct values for
characteristics such as voltage level, drive strength, and hysteresis. They do this by configuring a set of
registers from the IOMUXC.
For detailed information about each pin, see the “External Signals and Pin Multiplexing” chapter in the
i.MX53 Applications Processor Reference Manual. For additional information about the IOMUXC block,
see the “IOMUX Controller (IOMUXC)” chapter in the i.MX53 Applications Processor Reference
Manual.
13.1 Information for Setting IOMUX Controller Registers
The IOMUX controller contains four sets of registers that affect the i.MX53 registers, as follows:
• General-purpose registers (IOMUXC_GPRx)—consist of three registers that control PLL
frequency, voltage, and other general purpose sets.
• “Daisy Chain” control registers (IOMUXC_<Instance_port>_SELECT_INPUT)—control the
input path to a module when more than one pad may drive the module’s input
• MUX control registers (changing pad modes):
— Select which of the pad’s 8 different functions (also called ALT modes) is used.
— Can set pad’s functions individually or by group using one of the following registers:
– IOMUXC_SW_MUX_CTL_PAD_<PAD NAME>
– IOMUXC_SW_MUX_CTL_GRP_<GROUP NAME>
• Pad control registers (changing pad characteristics):
— Set pad characteristics individually or by group using one of the following registers:
– IOMUXC_SW_PAD_CTL_PAD_<PAD_NAME>
– IOMUXC_SW_PAD_CTL_GRP_<GROUP NAME>
— Pad characteristics are:
– SRE (1 bit slew rate control)—Slew rate control bit; selects between FAST/SLOW slew rate
output. Fast slew rate is used for high frequency designs.
– DSE (2 bits drive strength control)—Drive strength control bits; select the drive strength
(low, medium, high, or max).
– ODE (1 bit open drain control)—Open drain enable bit; selects open drain or CMOS output.
– HYS (1 bit hysteresis control)—Selects between CMOS or Schmitt Trigger when pad is an
input.