Configuration of THE SIU PCR register in MPC563X Series chips

[ZEROOO]

Hi，

    I would like to ask about the configuration of WPE and WPS bits in SIU PCR registers.When I configure GPIO input,I set the PA bit to GPIO, the IBE bit to 1, the WPE bit to 1, and the WPS bit to be configured according to the external pul-down circuit. At this time, the states of some ports read by the debugger are not what I expected. My question is how to configure the WPS bit and WPE bit when configured as input. Is the WPS bit invalid regardless of configuration when WPE is configured as 0 disable? If you want to configure WPS, is it based on the external circuit? If the external circuit is Pullup, it corresponds to Pullup, and if it is Pulldown, it corresponds to Pulldown?If you know, please tell me the specific configuration.

    Best regards,

    Zeroooo

[ZEROOO]

[davidtosenovjan]

WPS has the meaning only in case WPE = 1.

[ZEROOO]

Hi  David,

    When is the WPE bit configured to be 1? When I configured port as input, THERE were many problems with WPE configuration as 1. By checking the chip manual, I found that when configuring output, WPE bit was invalid no matter how it was configured.

[davidtosenovjan]

Sorry I don't understand you at all.

It is used mainly for INPUT function, because it defines level when the pin is not driven.

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. Voltage level is actively driven by push-pull circuits (unless open-drain enabled) and given by SIU_GPDO register.

[ZEROOO]

I'm glad you can answer my question.Actually, what I want to know most is when to set WPE bit to 0 and when to set WPE bit to 1. I am very confused on this question, can you give an example?

[davidtosenovjan]

WPE = 1, WPS = 1 => weak internal pull-up is enabled
WPE = 1, WPS = 0 => weak internal pull-down is enabled
WPE = 0, WPS = x => no pullup, input is floating and Hi-Z

Usage is application dependent as required by external connection.
Also it is recommended to enable pull-up/down on all unused pads. Otherwise I would point-out public resources.

[ZEROOO]

Can I understand this sentence "Usage is application dependent as required by external connection" like this?

If the external is pull-up circuit, WPE = 1, WPS = 1

If the external is a pull-down circuit, WPE = 1, WPS = 0

If the external input voltage is floating,WPE = 0, WPS = X

[davidtosenovjan · Accepted solution]

application dependent = it is up to you which pull configuration you are using

https://en.wikipedia.org/wiki/Pull-up_resistor

WPE, WPS configures weak INTERNAL pull resistors (intergrated in the MPC5634M MCU).