topic Re: How to clear CRC output register on MPC5643L? in MPC5xxx

How to clear CRC output register on MPC5643L?

fangfq — Mon, 24 Jul 2017 05:28:02 GMT

Hi,

I would like to know how to clear the CRC unit OUTP when I want to start a new CRC check sequence and abandon all the history values. This seems not an option based on the reference manual. Is it possible?

Or does the history value get auto cleared after the OUTP reading?

Thanks,

Re: How to clear CRC output register on MPC5643L?

petervlna — Mon, 24 Jul 2017 11:43:19 GMT

Hello,

This register is read only. Writes has no effect.

After reset it contains value 0xFFFF_FFFF

I expect that register is not cleared on read. I will verify it tomorrow in office and let you know.

Peter

Re: How to clear CRC output register on MPC5643L?

fangfq — Mon, 24 Jul 2017 18:39:37 GMT

I tested this feature with JTAG. And the CRC result is not cleared after the OUTP reading. So is there anyway I can clear the existing CRC result and start a new CRC calculation sequence?

Re: How to clear CRC output register on MPC5643L?

petervlna — Thu, 27 Jul 2017 06:43:45 GMT

Hi,

The CRC holds the last result values, until new check is started.

Then the last result values are overwritten by actual ones.

You cannot change it by clearing register.

Peter

Re: How to clear CRC output register on MPC5643L?

fangfq — Thu, 27 Jul 2017 16:17:58 GMT

Hi Peter,

Thanks for the reply. But how do you define "new check is started"? Can you give a more detailed explanation? It was not described in the reference manual. And if I start to write new data, the HW seems still calculate continued with the old value.

Re: How to clear CRC output register on MPC5643L?

fangfq — Mon, 31 Jul 2017 16:25:14 GMT

Hi Peter,

Thanks for the reply. But what is the definition of "new check is started"? Can you give a more detailed explanation? It was not described in the reference manual. And if I start to write new data, the HW seems still calculate continued with the old value.

Re: How to clear CRC output register on MPC5643L?

petervlna — Tue, 29 Aug 2017 12:00:53 GMT

Hi,

The new check started really means when the new check is started by SW within one reset sequence.

Peter

Re: How to clear CRC output register on MPC5643L?

medhedibasly — Fri, 15 Mar 2019 13:18:46 GMT

I recently worked on a SW driver for the CRC unit on MPC5748G, i faced the same problem and i found a way to solve this.

when i get the final CRC value i clear the INP register by writing 0x0000000 to it, then i clear the CSTAT register by writing 0xFFFFFFFF, this clears directly the OUTP register and you can restart a new CRC calculation without resetting your MCU ☺.