 Hi, I'm MPI. Hi, I'm MPI, I'm brought to you by DigiKey and Adafruit. Thanks DigiKey. This week it is from ISSI. What is the new product introduction of the week? This week. OK, ISSI. I love their LED driver chips, but they're also famous for their flash memory. And this week we're going to talk about memory. In this particular case, we're talking about PS RAM chips because digikey.com highlighted their serial and parallel memory chips. And what come I, in particular, was their 8SOIC package, Q-Spy slash SPI, PS RAM available in 1.8 volts or 3 volts, 3.3 volts. Logic in power, 100 megahertz speed with burst output available in a couple of different packages. But basically, perfectly designed for chips that need, or sorry, can take advantage of PS RAM, which is more and more chips these days. So if you remember back in the day, the ATMEGA328 was like an amazing chip. This chip came with an 8-bit processor, 32 kilobytes of flash, 2 kilobytes of SRAM. That was amazing. We loved it. It was so spacious compared to the 32 bytes or 64 bytes we were used to. But that isn't even really enough anymore these days. We need more memory, more flash, more RAM. And one of the issues with chips, I thought this die shot was great because you can see sort of, it's not a RAM bank, I think it's the cache on the side, but you can imagine it's a RAM bank or a flash bank on the side. When you buy chips, you know, you're buying pins and you're buying processor speed, you know, like your Cortex M0 is going to be less expensive than an M4, which is less expensive than an M7. But you know, the more processor speed, the more you pay, the more pins the more you pay and the more flash and the more RAM you pay. The problem with flash and RAM is that, you know, if it's built into the chip like here, this is an RP2040, it takes up a significant amount of space. And so chip manufacturers want to optimize the amount of space used because you pay for the die size. They don't want to include more SRAM or flash memory than they can get away with, kind of the less they can get away with, the better because they have a smaller die, they don't have to, you know, they get more chips per wafer, their yield is better, et cetera, et cetera. So for example, you know, one thing we've noticed lately with chips, especially the RP2040 is, for a lot of people, the first Mac controller that does this, there is no flash memory on the chip. There is, as SRAM, but there's no flash memory because you're expected to attach the flash memory using a QSPY chip, like this one, ISSI also makes tons of them, the SL25 series. You can attach the QSPY port on like the RP2040 and then you can pick any size flash chip from, you know, as little as 512K up to 16 megabytes, which is a lot. And, you know, you pay a little bit more for more memory and you do need more board space, but the RP2040 doesn't have to come in like 15 different versions. Like, you know, that mega has like different sizes for every chip because you might want more RAM or less RAM and you have to pay for it. So you have like this wide range of chips with the RP2040, they're like, now we're only gonna make one chip and you choose how much flash you want. And then, you know, likewise, a lot of microprocessors, historically, you know, you'd have an external flash chip, you'd also have an external RAM chip. Like, for example, you'd have sort of like a parallel DRAM. So we're taking apart, you know, my, you know, Palm 3 and it had, I think I like a Motorola Cold Fire chip and there was, you know, flash memory. And then there was the DRAM, which was, you know, kind of looked like this, it was a T-SOP chip. It probably had like, you know, maybe one megabyte of DRAM. But the problem is that these DRAM chips, even though they're really popular and they're used in, you know, embedded Linux and embedded processors, you know, ARM, you know, the ARM 7 series, TDI series and higher, you need a lot of GPIO because they often have, you know, 8 to 12 address pins and then they have like 816 or even 32 data pins. So these are for processors that are like BGA and have, you know, 168, 144 GPIOs. It's no big deal if a quarter of them are lost to the DRAM interface. And you also want very, very fast RAM. But for chips that are smaller, like for example, like this ESP32, only has, you know, 44, 56, maybe 64 GPIO. You can't have 32 pins for the SRAM and for the flash memory. So like the RP2040, the ESP32 doesn't have built-in flash or it has a very little, you know, maybe some ROM. It has some onboard SRAM, but only like 300K. And if you want to use, you know, the ESP32 series to read large buffers or use TLS so you're encrypting stuff, you're gonna quickly run out of memory with that 32, 320 kilobytes. You really need like a megabyte or two to read images from a camera, to buffer a display, to hold fonts, to hold, you know, like I said, JSON data for posting to or from internet connectivity or proto buffs or whatever. You know, if you're gonna do these kind of IoT projects, you're gonna need PSRAM. And so more chips like the ESP32 and also the IMX series also supports PSRAM. There's a data sheet here where you tell it basically, you know, these six pins are connected to external QSPY RAM and I want you to read it on boot and then integrate it into the program. And so the program sees it as like a continuous chunk of memory. It's slower than the onboard SRAM, but again, you wanna like, let's say you have your TNC 4.1, you wanna buffer a gigantic waveform because you're making some cool synth project. You need a couple kilobytes for each waveform before you know it, you know, you want maybe 32-bit resolution. You're gonna use a lot of memory. You need a one megabyte of PSRAM and you can solder it on the bottom. You can see on the left there, there's two spots, one for flash memory and one for PSRAM if the internal SRAM isn't enough. And the good news is that PSRAM uses kind of a standard interface. So if you have a chip that uses PSRAM, this is the pinup for the ISSI PSRAM, it's good to go. And then you will need to tell your compiler or your tool chain, hey, you know, PSRAM is attached to these pins and you might have to tell it the command names, especially for like quad IO read and write or to put it into quad mode. Sometimes there's like a special, the bit for where you set the quad bit is in a certain location. Like you see, says enter QSPY mode. Sometimes that varies from chip to chip. So you do sometimes have to configure it. So don't be surprised. It's like, oh, I started the chip up and it didn't immediately work. You probably have to like change some setting in the make file. Good news is that like ISSI is, you know, very popular, very prolific maker of memory. And so if you have a chip that supports PSRAM, they probably already have a configuration file for ISSI. And they're available in a lot of different sizes and voltage levels. So there's the ALL series, that's 1.8. The BLL series, that's 3.3. And then various packages and density. You know, I think I looked in Digikey stocks between one megabyte and up to, I think, 16 megabytes of PSRAM. So you can have like a huge buffers for, you know, data capture, you know, it's not gonna be, you know, one nice thing that's about PSRAM is that, especially if you're doing data capture, you want to grab a lot of information from like a DAC or from an ADC or whatever, is you're not gonna have the page erase issue with SPI flash, and you're not gonna have the high expense of FRAM. So as long as you're okay with, you know, the memory being erased when the power is lost, which, you know, PSRAM is dynamic, you can have gigantic data buffers for like only about a buck or two. I would suggest, if you're like, which one do I start with? Two megabytes, 16 megabytes is a good place to go. Check this out. The IS66WVS2M8BLL, getting up to 100 megahertz nice and fast. Two megabytes of memory for about two bucks. That is this week's IonMPI. IonMPI.