Introduction

Hello. This is Tott, who is steadily accumulating circuit board knowledge as an engineer.

One day, while providing customer support regarding memory, I saw a senior engineer struggling to help, and I wondered, "What exactly is memory?"

I think

Beryll – Tested on the Cyclone ® V GX baseboard.

Just looking at the circuit board, there are so many devices that it's hard to tell which one is the memory. After investigating, I found that it has SRAM, DDR3, and EPCS installed.

SRAM : IDT

As a rookie engineer, seeing this left me completely bewildered, so I decided to do some research on memory.

What is memory...?

As a rookie engineer, I thought, "Memory... memory... recollection...?" and looked it up, and it turned out to mean exactly that: "recollection."

Memory is a place where data is stored.

The following are some of the most common types of memory:

(Note) The above diagram is an example.

The EPCS ROM and EPCQ ROM/EPCQA ROM used in Altera's FPGA device configuration are classified as FLASH ROMs in the diagram above.

The senior engineer in charge was struggling with a type of memory called DDR3-SDRAM, which is classified as DRAM in the diagram above.

So I decided to look into DDR3-SDRAM.

Positioning of DDR3 in DRAM

After examining DDR3, I found that DDR3 is positioned as shown in the figure below in DRAM.

It turns out that the data transfer speed is getting faster as the generation is newer.

* SDR stands for Single Data Rate.

Data is transferred at the rising edge or falling edge of the clock.

* DDR stands for Double Data Rate.

Data is transferred on both the rising and falling edges of the clock.

Role of DDR3-SDRAM for FPGA

・Temporarily saves the data processed by the FPGA. (light)

・Read the temporarily stored data and process the data on the FPGA. (lead)

short story

Me: "Temporarily save? What is the difference when saving to HDD? ’ I thought, and when I asked my senior,

Senior colleague: "When interfacing an FPGA with an HDD, processing data takes longer compared to RAM or ROM."

Me: "So that's why PCs are slow when the HDD acts as virtual memory!" I finally understood.

By the way, what is the principle of read and write operation of DDR3-SDRAM?

Summary of this time

■Memory is a place where data is stored.
■DDR3-SDRAM temporarily stores FPGA data.

Go to next time...