51AC and CRCV2

[SoJulien]

Hello,

I use the MCF51AC256 processor and I make an application with verify an I2C memory checksum.

I want to use the hardware CRC because the memory size which must be compute the CRC is 4 kByte.

I make a little application (DemoACKIT board) to show my problem :

this application changes the state of one LED every seconds and at each changement state, the application computes alternately Hardware CRC and software CRC.

When I don't activate the hardware CRC, LED blink correctly (every second)

When I activate the hardware CRC, the CRC function compute a correct CRC (compared to Software CRC) but the LED is fixed at state on or off, it's very strange.

In this case when I execute step by step the CRC, I remark that some register are modified.

I don't understand what happen.

If somebody already use the hardware CRC on this Coldfire, can he answered me and correct my application ?

Thank you.

Julien.

[SoJulien · Accepted solution]

Ok, matter found thanks to Freescale support.

Origin : the mcu used was a "PCF51AC" with mask "0M60N"  that as a mask error compared to MCF51AC for the CRC function.

Workaround from Freescale support :

" 

SE154-CRC-Affects-Content: CRC Affects Content of Direct-Page and

High-Page Registers Description: CRC affects the content of the

following memory ranges: 0xFFFF8000 to 0xFFFF80EC (Direct-Page

Registers) and 0xFFFF9800 to 0xFFFF98CF (High-Page Registers)

interfering with several MCU peripheral configurations. The error

happens when any data is written to the CRCL after the seed was loaded

to CRCH:CRCL. Workaround: Load the SEED value to CRCH:CRCL, perform the

CRC computations (that means reading from RAM or FLASH and writing to

CRCL; at this time, reads from Direct-Page/High-Page will be affected)

and finally read the CRC result from CRCH:CRCL. Then, once the CRC

module will no longer be used, one additional step (workaround) would be

to write 0x00 to CRCH and 0x00 to CRCL. As a result, the

Direct-Page/High-Page positions should not be affected anymore.

"

Thanks,

Bye,

Julien

[SoJulien]

Hello,

Note that in fact the hardware CRC crash the register at the first time the CRC Generator is being used.

Putting the call to "so_HardwareCRC_Compute();" in comment and led 1 flash every second.

Then activate call to "so_HardwareCRC_Compute();" --> mcu crash !!!

This is seems for example while looking @ 0xFFFF8000 (PTAD register for port A) that is not used on this function and that is modified after the first CRC instruction : "CRCH = 0xFF;" in "void so_HardwareCRC_Compute(void)"

After that some instruction execute for CRC function (during some luky state) then program crash.

I do not see any help in AN3795 or in RM, so any help is appreciat, thanks.

Thanks you,

Julien,