MPC5777m DCF Client Configuration

[johnramoul]

Hello all, 

I am currently working with the MPC5777m and would like to configure my GPIOs to a 3.3V instead of 5V. In the Datasheet it mentions the following: 

"In order to use 3.3 V on the VDD_HV_IO_MAIN0 physical I/O segment, the HV supply low voltage monitor (VLVD400)
must be disabled by DCF client." 

I am very lost on how I am supposed to reprogram the DCF Client records for the MPC5777m such that i can get a 3.3V GPIO.

I am using the MPC5xxx Motherboard and 512DS daughter board which as of hardware it seems simple to just switch from the 5V SR supply to 3.3V SR supply. I have also configured the necessary PMCDIG.VSIO.R register to accept 3.3V for my GPIO but when i switch the jumper to 3.3V the microcontroller becomes in reset mode and I cannot program it anymore. 

Any help is appreciated,
Thank you.
Sincerely John Ramoul. 

[petervlna]

Hi,

I will make it easier for you.

You can run IO on 3.3V but you can only disable 4V LVD via SW write to PMC.REE register.

And you must run the device on 5V after reset. Then in SW disable 4V LVD and then you can swith IO to 3.3V.

You cannot run IO on 3.3V from start.

Reason:

PMC 4V LVD is by default enabled. If you apply the 3.3V on IO then you will get reset immediatly from 4V LVD before you can reach phase where DCF records reconfigure device.

I will try to explain it on following picture:

Hope now it is clear,

Peter

[johnramoul]

Hi Peter, 

Thank you for your response. This has been challenging for me. 

From what I am understanding I do not need to alter the DCF records to make the 3.3V IO Functional? 

I have set the following (Currently Avoiding writing to DCF Clients): 

PMCDIG.VSIO.R = 0x00000000 ; // Setting Main I/O segments to 3.3V supply
PMCDIG.REE_VD13.R = 0x00000000 ; // disabling PORST for 3.3V undervoltage for I/O
PMCDIG.REE_VD14.R = 0x00000000 ; // disabling PORST for 3.3V undervoltage for I/O

Does this mean I have to set these values during phase 1 of the Reset State Machine or do I have to set these values after Reset during Application execution?  Once I have set the above values is it valid for me to switch the jumper from 5V to 3.3V without having the MPC5777m to reset? 

Also, What if I want to run my Microprocessor directly from 3.3V on a standalone board? How can I manage to have a startup of 3.3V? 

[petervlna]

Hi,

it is exactly as I have described in previous post.

1. you always must have 5V present after power on reset

2. DCF records are useless in this case (just don't use them)

3. When you application is running you have to use SW to disable LVD400 (4V LVD) in PMC.

4. Now you can lower your IO supply yo 3.3V.

5. You cannot run your board only from 3.3V. Reason is described in picture I have posted above.

Peter

[jschloss]

Is this configured in PMCDIG_REE_VD14? The reference manual states "If the flash loaded bits are programmed to be enabled (set), these bits cannot be disabled (cleared) .", which makes it sound like we can't clear them at runtime if they are set - but it looks like I can clear them (just looking in the debugger, I haven't tried to lower the IO supply yet.

Do we need to disable LVD360 as well as LVD400 to get 3V3 IO?

Thanks,

Jacob