Explanation of the pad control functions in the Freescale processor?

Question

Reading the MCIMX50 processor reference manuals on page 1368 (section 33.3) is a list of the various possible management options for the processor sites.

List:

• SRE (1 bit slew rate control).
• DSE (2-bit voltage control).
• ODE (1 bit open drain control).
• HYS (1 bit hysteresis control).
• PULL_KEEP_CTL (4 bits to pull up / down and controls).
• PUS (2 bits pull up / down configuration value)
• PUE (1 bit / save selection)
• PKE (1 bit enable / disable pull up, pull down or keeper)
• DDR_MODE_SEL (1 ddr_mode control bit)
• DDR_INPUT (1 ddr_input control bit)

Can someone explain that each of them, preferably in an educational manner with links to additional information?

Thanks in advance.

Answer 1

SRE (1 bit slew rate control). How quickly the state of the pin changes from 0 to 1, since rapidly changing states consume more energy and emit bursts of RF, slowing it down if you can help EMC. We run most of our GPIO pins at low slew rates, except for SPI and I2C, which should be fast.

DSE (2-bit power control). - How much current the IO pin will be a source / stream, again an energy-saving / EMC device, since in general it is a bad practice to hang loads directly from micro ports.

ODE (1 bit with open drain control). - Regardless of whether the pin drops to 0 V for a low output or if there is an “open drain” (disconnected / floating), this is useful for some things, such as I2C, where the parts rotate in order to keep the lines low or high .

HYS (1 bit hysteresis control). - Look at the hysteresis on Wikipedia, tell you everything you need to know.

Pullups / downs etc. - basically, does the pin have an internal resistor connected to + v or 0v to stop everything that floats to some random / unwanted value, usually used when the pin is an input.

DDR_MODE_SEL (1 bit control ddr_mode) - possibly a data data register, in other words, it is output or output

DDR_INPUT (1 bit ddr_input control) - Not sure if the micro link guide should give you some idea about this and everyone else.

Hope this helps!

Answer 2

This is described in detail in note AN5078 of the application for the Freescale website.

Link: http://cache.freescale.com/files/32bit/doc/app_note/AN5078.pdf

Summed up: The keeper keeps the output level the same, even if you turned off the driver. There, an internal resistance of ~ 130 kOhm is connected there, so it will not travel much, but it will keep the pin from swimming.