Hello,
we are currently testing the external RAM of the MPC5777C-516DS using the provided example software (https://community.nxp.com/t5/MPC5xxx-Knowledge-Base/Example-MPC5777C-External-SRAM-test-GHS714/ta-p/...). It runs fine although bursting is not enabled which we want to use for our application.
To enable bursting we changed the following settings:
- The burst inhibit flag was disabled and a 4-word-burst was configured:
EBI.CAL[0].BR.R = 0x200000C1
- Further the cache was enabled for the MMU entry:
se_bgeni r3,2 // virtual address at 0x2000_0000
e_ori r3,r3,0x0030 // VLE, cache-enabled, write through
mtspr MAS2,r3 // Load MAS2 with 0x2000_0030 for TLB entry #2
To check if the external RAM is working we implemented a simple test:
- First we write data to the whole memory area using a loop that iterates over all DWords.
- Then we read the data back and compare it to catch any errors using a loop that iterates over all DWords.
But something peculiar happens when executing the test: Wrong data is read from the external RAM in the loop that checks for errors. When we set a breakpoint in it we also see the wrong data in the memory dump of the TRACE32-debugger. However, after the execution of the loop is finished the dump shows the correct data. This leads us to assume that the problem is caused by caching but we were unable to find a solution.
Is it possible to use burst accesses with the EVB? If yes, could you please provide the settings that have to be used for the hardware present on the MPC5777C-516DS?
Regards,
Bernd
