nonvolatile SRAM???

[deng]

Posted on May 06, 2004 at 03:26

nonvolatile SRAM???

[deng]

Posted on May 17, 2011 at 12:00

Hi All,

I am wondering how to access the SRAM correctly. We are using the uPSD3254BV and it has 32K SRAM. Our problem is not that we are not able to write to the ram but why are the Xdata appeared to be nonvolatile. We have a program in Keil to map the variable foo_xyz at X:0803H which we thought are the Xdata space for static ram (SRAM). It turns out that when we powered-down our system, the value of foo_xyz didn't changed. I think Xdata could be volatile or nonvolatile. But I still dont understand where exactly are the 32K static ram go. I already review the example 2 (USB) from the UPSd eval kit, which didn't answer the above question. Any idea how to resolve this? Regards, SD

[danielh1]

Posted on May 17, 2011 at 12:00

Do you a DK board? it has a battery backup integrated with the real time clock.

Daniel

[deng]

Posted on May 17, 2011 at 12:00

No, we are using our board. There is no backup battey in our RTC.

SD

[lwang]

Posted on May 17, 2011 at 12:00

I think the SRAM may retain the contents after you switch the power off for two possible reasons. One reason is that the capacitor(s) on the Vcc line may have residue voltage that can keep the SRAM alive for quite a while. The other reason is the JTAG or other connection may leak enough current to keep the SRAM alive. I suggest that you (a) write something to SRAM, (b) turn off power, (c) disconnect JTAG or other connections, (c) wait for quite a while, and (d) reconnect, power up, and read SRAM.

BTW the battery on the evaluation board only keeps the RTC alive, it has nothing to do with SRAM in the uPSD.

[deng]

Posted on May 17, 2011 at 12:00

Thanks guys, removed the JTAG cable and power down the system did show the SRAM resetting.