An Overview and Demo of the Cypress F-RAM Technology

See how Cypress’s serial F-RAM memory products provide an effectively unbreakable endurance of 1016 over EEPROM’s 106, perform page writes that are five thousand times faster, and operate with a lower power level of 3mA over EEPROM’s 10mA. You can also see how to put it all together with a detailed demo training for the PSoK® 4 Pioneer Kit with a tutorial for loading the software.

Hi, I'm Grant Hulse with the F-RAM Marketing Team here at Cypress.

Today, we're going to use the PSoC 4 Pioneer Kit with an adder board that will showcase our serial F-RAM memory products. F-RAM stands for ferroelectric random-access memory. It has three key advantages over an EEPROM. First is endurance.

Now endurance is defined as the number of times a nonvolatile memory cell can be rewritten before it wears out. For serial EEPROM, that number is about a million times. That works out to about two years if you write to a certain address every minute or two weeks if you write to the same address every second.

Now compare that to an F-RAM. F-RAM's endurance number is 100 million times higher or 100 trillion, that's 10 to 14th, that's millions of years if you write to the same memory location several times each second. This makes the F-RAM technology effectively unbreakable. Second is speed.

 Any write to a serial EEPROM takes a very long time. They usually group together a whole page of memory and then write it all at one time. This takes many milliseconds. F-RAM is different. You can write a single byte or a few words at 40 megahertz clock speed, which is over 5,000 times faster than similar writes to that EE. Even when replicating the EEPROM's function and writing full pages at a time, our F-RAM product can do those page writes 200 times faster.

Third is power. Not only is it faster and more nonvolatile, it also offers these features at a much lower power or current level. This makes F-RAM the most suitable solution for anything needing ultra low power, like handheld battery operated applications. We're now going to go through a detailed discussion on setting up the demo and getting the software loaded.

So I recommend you have your demo kit and your PC right in front of you at this point. This is the demo board. It clips onto the top of the PSoC 4 Pioneer Kit. On the bottom of the board, you can see the four connectors J1 to J4. These line up with the connectors on the Pioneer Kit. Just line up the four connectors and seat the F-RAM board on the Pioneer Kit board.

Here is the assembled demo. The demo board is mounted to the Pioneer Kit. This switch 1, SW1, powers the two sockets separately, so please put it on off position for now. I've connected the USB cable but just to the Pioneer Kit so you can orient your board. I haven't connected it to the PC yet. Our board has two sockets here on the top.

One is for an F-RAM part and one is for an EEPROM part. This is so we can do side-by-side tests that compare the technologies. The 256K F-RAM is here in this socket. This particular F-RAM is an S-P-I or SPI, or serial peripheral interface part, but you can switch it to an I-squared-C part, change densities, etcetera.

The sockets are for 8-pin SOIC packages. We send several of these F-RAMs along with the kit. With the USB connector at the bottom, the top mark letters on the package are right side up and pin 1 has a dimple. The F-RAM IC goes here in relation to this USB connector. The socket is spring loaded.

Once you place the IC, push the socket down, then let it up, and it will grab the leads. The second one is a 256K Serial EEPROM. A few of these also came with the kit. This has the same spring loaded socket. Now go ahead and pause the video until you get the kit assembled as I've shown you to this point.

Now that it's assembled, we are ready to hook it to the PC, download the software, and run our demos. You can now turn switch 1 to the on position. Again, this allows power to the two socketed parts. And plug the USB cable into the PC. These three status LEDs will come up like this, and the demo board is ready to run. Pause the video here until you get to this point.

After you install the demo software, go to Start > All Programs > Cypress then look for the "Serial SPI F-RAM Demo" and click and open that demo. That should open this demo screen up.

Okay, that works.

Let's close this demo screen again for right now. Now we're ready to load the .hex file and configure the demo board. Again, go to Start > All Programs > Cypress  and open PSoC Programmer. I have 3.20.0. Make sure you're connected to the board in the bottom right. Then select the hex file you have saved on your local drive, and click the program button.

There. We're ready to run the demos. Let's look closer at the demo screen. Open it up again. There are four sections on the screen. The Device Settings section, top left, the Test Panel section that shows our three test choices in the bottom left, and the F-RAM Data Results and the EEPROM Data Results over on the right side.

Let's review the Device Settings. U1/U3 is the first socket where we put the F-RAM IC. U2/U4 is the second socket where we put the EEPROM IC. Both these parts are 256K bit, so the density is set correctly at 256. The page size of the 256K EEPROM we supplied you is 64 bytes. The Write Delay can be set between 0 milliseconds and 10 milliseconds.

EEPROMs have a worst case write file of 5 milliseconds. We will vary this number in our tests. For Write Data Byte, we only need to set this first box to any number between 00 and FF hex. When we do that and click out of the box, the inverse hex number shows up in the second box.

These are just test patterns we use the hex number and its inverse for to fill the full memory during these simple comparison tests. Let's now look at the Test Panel. Here we see three different tests we can use to show F-RAM's value over EEPROM. The Write Delay Test, the Throughput Test, and the Power Fail Test.

First, I'll show you the Write Delay Test. This test runs the same data at full speed into both the F-RAM and the EEPROM devices. The F-RAM is going to catch all the data without any errors because of its superior speed while the EE is going to miss most of the data because it has to wait for each page of memory to be deleted before a write can be done.

This page delay is, worst case, 5 milliseconds. I'll show you what this looks like. We'll set the Write Delay to 0 milliseconds. In other words, there will be no delay between page writes to the EEPROM which does violate that part spec. I'll put hex 55 in the Write Data Byte. The complement data automatically will calculate to AA hex.

Again, you can put any hex number in here for any test. Just change the number to put it in between each test you run. Execute the Write Delay Test by clicking the Write Delay Test button. Let me do the math for you. With 64 bytes in a page, there are 512 pages of EEPROM in a 256K part.

The results show the F-RAM caught all the data, all green. But the EEPROM only wrote 86 pages of the 512 pages correctly because we did not allow the slower EEPROM part to clean each page between the writes. Now let's run the test again and give the EEPROM a bit more time.
Let's set the page delay to 1 millisecond. This is still too fast for the EEPROM, but it should be able to get more data into its memory with this bit of help. I randomly changed the Write Data Byte to 33 hex, the complement data becomes CC hex. So the test can get a fresh comparison.

This time again, the F-RAM is all green, the EEPROM has done better also, but even with 1 millisecond delays, the EEPROM cannot capture all the critical data. Finally, we run it one more time. Let's follow the EEPROM spec this time and set the Write Delay to 5 milliseconds.

This will give the EEPROM the time it needs to complete its page erase and rewrite processes. I randomly again change the Write Data Byte to 66 hex. The complement data becomes 99 hex and we execute. Now look, the EEPROM is catching all the data and is green and fast like the faster F-RAM parts.

Another speed comparison test we offer is the Throughput Test, the Throughput Test is like a car race. Both memories are filled as fast as possible. The faster memory, the F-RAM, crosses the finish line first when the memory is fully written. The EEPROM crosses the finish line much later when it finally has all its memory written.

To execute the Throughput Test, set the Write Delay to 5 milliseconds. This Write Delay is only for the SPI EEPROM so it can meet its operation spec. Again, I change the Write Data Byte, let's say 77 hex, and the complement is 88 hex. I click on the Throughput Test button.

After the test completes, you can see that the total time to write the F-RAM is about 0.16 seconds, and the EEPROM is about 2.7 seconds. So that means the F-RAM is 16 times faster to fill than the EEPROM. Actually, this is a limitation of this demo kit.

By spec, the F-RAM is really 200 times faster than the same size EEPROM. So this is a really cool test to show. The third and final test is the Power Fail Test. The Power Fail Test looks at the last moment of data storage, the moment when power is suddenly lost.

Since an EE has to hold a full page of memory for 5 milliseconds before it can complete its store, that full page is at risk. It will be lost on any power interrupt. An EE design has to include a battery or a large capacitor to hold the EE up long enough to complete its last store, or that last page of data will be lost forever.

F-RAM has no delay. So we save the last complete byte of data received without any battery or any capacitor. To execute the Power Fail Test again, write the write data to 5 milliseconds for the EEPROM, and again, change the Write Data Byte to anything you want. Click on the Power Fail Test button and wait for the yellow LED to blink several times then turn off.

This indicates that the demo setup is ready for the Power Fail Test. Now turn off the power supply by switching this on/off switch on the F-RAM board to the off position. After switching it off, notice that a result window that shows the last writable address is on the screen.

Power on the demo by moving the switch back to the on position. Now let's look at the result window. The F-RAM result window shows all greens indicating the expected data was written to the F-RAM and saved correctly. But there is one page, that last page, 64 bytes of data on the EEPROM that were lost.

This is shown by the single red line in the results. Again, an abrupt power fail in a system can corrupt the data in a full page of an EE, while all the data is always safe in the F-RAM.

Well, that completes the Serial F-RAM demo training. I hope you enjoyed it. Remember, if you need fast writes or lots of writes, please look at the F-RAM product, it has lots of very cool features. 

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