Electrical Engineering

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Why are DRAM cells laid out in a square with regards to demux size?

I'm reading the chapter about DRAM access (2.1.3) of the paper "What Every Programmer Should Know About Memory - Ulrich Drepper" and there's a certain snippet that I just can't make sense of....
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1answer
186 views

Why are SDRAM CAS latencies so high?

I don't understand why the CAS latency of modern DDR4 memory is so high. I have no trouble understanding why the RAS latency is as high as it is -- given the small amount of charge stored in each ...
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1answer
60 views

SDR over DDR memory in FPGA based design

I am designing a new project which demands the usage of DRAM. I have never interfaced with one before, so my knowledge is rather limited. By analyzing the requirements, it would be sufficient to go ...
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2answers
104 views

How is 1 bit transfered from RAM to a 1 bit register?

I've been reading on computer RAM and CPUs. I came to the conclusion that most RAM today use arrays of DRAM while CPU registers and caches use SRAM. 1 bit DRAM is a circuit with one capacitor and 1 ...
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1answer
76 views

DRAM Rank-Level Allocations

I want to do allocations on a specific DRAM rank. The smallest allocation unit in an OS such as Linux is at the page size ...
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34 views

Termination Requirements for DRAM

I am curious about how to wire DRAM to an SoC. What is required for optimal usage other than the net itself? I have seen conflicting information on if you should or should not use a termination ...
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1answer
75 views

Can i make dram using bjt transistors? [closed]

Is it possible to make dram using bjt's or is it only possible with mosfet's? If not why not? Is there an advantage in using mosfets instead of something like a bjt ?
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3answers
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DDR: Is the real maximum speed half of what is advertised in datasheets?

Let's take a single 8-bit 200MHz DDR chip. All datasheets state that bandwidth is "up to" 400MB/s. Because it's dual, data is read/written on both edges so yes, theoretical, it's 400MB/s. ...
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1answer
33 views

ddr: Is there any significant delta between the different strobes?

In a DDR memory, during a read, output data from the DDR is aligned on the strobe. There is one strobe per 8-bit: UDQS/LDQS for a 16-bit-wide DDR DQS[0-3] for a 32-bit-wide DDR Is there any ...
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1answer
86 views

No terminations on point to point DDR3?

Are terminations required for DDR3 in point to point designs? I saw a reference design that doesn't include any termination to VTT for a controller/single DRAM design (pt to pt). DQS, DM and DQ use ...
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53 views

DRAM Self-Refresh not the Lowest Power Mode

I have a DDR3L Samsung DRAM on my Laptop. Based on page 23 of its datasheet, IDD6 or the ...
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0answers
33 views

DDR3 AC characteristics

What is the meaning behind different AC input levels such as AC120, AC135, AC175 etc? I understand that AC_X means the level is Vref + X mV. And I also understand that the setup time is defined with ...
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1answer
58 views

Is an even number of DRAM chips required?

I want to design a microprocessor based board (NXP imx 8m). All the boards I've seen so far have an even number of DRAM chips. If I want 4GB of RAM, do I have to use two 2GB DRAM chips or can I use ...
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1answer
77 views

Can you get “raw” TFT display panels where you drive the gate and drain lines directly?

I am learning about different display types and how I might interface them with raw electronic components, e.g., TTL chips, op amps, function generators for scan line sawtooth, etc. CRT raster is ...
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2answers
57 views

Is DRAM burst mode compatible with bank interleaving?

I am trying to understand how DRAM burst mode is compatible with bank interleaving. Once a row within a DRAM memory array has been activated, sensed and buffered, according to the strobed row address,...
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1answer
50 views

EEPROM converted to DRAM?

Can we use a EEPROM cell for DRAM ? simulate this circuit – Schematic created using CircuitLab This is an EEPROM cell. Can we use multiple cells of this type to create a DRAM?
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68 views

How to design 1T-1C DRAM circuit in spice design tools, such as LTSPICE?

I have been trying to design a DRAM cell using the LTSPICE MODEL tool. The DRAM that I want to design is of 2nd GENERATION, i.e, 1t-1c dram cell. But whenever I design digit line it states the line is ...
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75 views

On DRAM timing, why tWTR is larger than tRTW?

If I understand correctly, tWTR includes both bus turnaround time (between memory controller and DIMM) and safety margin to make sure that data are written to target row buffer before read operation ...
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1answer
189 views

Why cant clock be directly used instead of DQS in DDR during read and write

I have been reading about DDR lately and I am not able to understand the exact use of the DQS signal. The timing diagrams show dqs in phase with clock so why cant the clock only be used for the write ...
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59 views

open source SATA to DDR2 SDRAM adater

I want to learn how computer memory sticks can be used as secondary storage using some intermediate FPGA for data processing. Actually I want to design a PCB myself. I'm good with PCB designing but I ...
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2answers
70 views

How to reset flip flop in ATF16V8?

I'm designing a Z80 microcomputer with dynamic memory (DRAM), and I want to control the memory with 3 chips; an ATF16V8 Generic-Array Logic, and 2 74LS157 quad 2:1 multiplexers. The logic diagram of ...
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0answers
34 views

Find capacitor voltage for dram cell!

I have a mosfet with Vin connected to drain e constant voltage applied on Gate and a capacitor between the source and ground. I believe this is a dram cell. Vo=0 for t<0,Vg=Vstep(constant) and Vth=...
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1answer
112 views

Why do we need interleaved memory?

I am trying to understand the DRAM working paradigm. I just read this article about interleaved memory. It says: Interleaved memory results in contiguous reads (which are common both in ...
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1answer
152 views

The detailed working steps of the DRAM 3T1C cell?

This question is related to this one. But the focus is a little different so I put it here. I tried to understand the detailed working steps of below circuit. It is an old 3T1C DRAM cell circuit. ...
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2answers
103 views

Why is reading the 3T1C DRAM cell not destructive?

Could anyone help explain how the above 3T1C DRAM cell works? T means transistor and C means capacitor. Why is reading it not destructive?
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1answer
124 views

DDR4 board bringup issue

I am struggling with a DDR4 related board bringup issue. Can anyone out there recognise what the problem is by studying the attached memory dumps? The memory dump is from Preboot loader PB31 area of ...
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1answer
35 views

Can I use IS42SM16160K DRAM instead of IS42S16400 DRAM?

I have designed a custom board based on the STM32F4 controller and IS42S16400 DRAM. For some reason, I want to use IS42SM16160K mobile DRAM instead. Should there be a change in programming and ...
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1answer
67 views

DRAM late and early read and write

For read operation in DRAM, perform early read mean OE low before CAS is low so doesn't this mean that you just read in junk data ? For write operation, i don't think there any problem with early ...
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54 views

DRAM Memory Lines

I have been trying to understand DDR and DRAM memories and stumbled upon this video In this video, from 20:00 to 23:00 he tells that the 8kb row buffer lines, actually come out as 64b and this 64b ...
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2answers
1k views

What is the difference between DRAM channel and DRAM Rank?

Can someone explain me the terms : DRAM Rank and a DRAM Channel is simple terms. I went through this PDF and I was not able to understand the DRAM Organisation/architecture on page 3 and page 11. Can ...
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2answers
73 views

Running code from different storage

So i know this question is being asked almost everyday on thousands of forums, but i am still going to ask that same question but with a different intent. Question #1: As an example lets use linux ...
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1answer
130 views

LPDDR4 pre-fetch

In the JEDEC LPDDR4 spec it is mentioned that LPDDR4 DRAM can support burst length 32(BL32) and also the LPDDR4 DRAM architecture is 16n prefetch. I want to know how burst length 32 be possible with ...
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1answer
136 views

Latch-based sense amplifier design using CADENCE Virtuoso 65 nm technology

I am trying to design a latch-based sense amplifier to sense about 55mV voltage difference using 65nm technolgy, it takes differential input, and should get from it differential output too where it ...
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1answer
46 views

Where the appropriate word size is selected for the operand?

This question is about a 32 bit Intel Chip using x86 assembly. My question specifically is what happens when you do the mov reg, mem instruction where the memory operand is a word (16 bits) from DRAM. ...
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1answer
1k views

RAM Row and Column Decoders

I keep seeing similar diagrams of RAM like this abstract picture of a simplified RAM Layout. So I just arbitrarily selected this picture but my question is about this layout in general. My ...
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2answers
147 views

What design differences make ram faster than ssd for read/write [closed]

I understand that RAM is connected directly to the CPU via a high bandwidth bus, and SSD is a peripheral, but my assumption is that there are also electrical design differences (e.g. memory cell ...
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1answer
111 views

DRAM in a FPGA - Image Sensor design

I am designing the simplest form of a camera: an FPGA that interfaces an image sensor and sends the acquired data to the host device via USB 3.0. There is no processing on the FPGA, it is used for ...
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47 views

When do we actually need bank interleaving?

Since common DRAM chips support burst transfer and hardware page size (row size) in a bank is quite large, we can amortize the charging & activating time over bytes in a long burst transfer. I ...
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2answers
914 views

GPU vs CPU on chip memory

There has been a fairly wide ranging discussion as to why it is difficult to combine memory / CPU logic on the same die (yield issue compounding, different processes, different clock-frequency, ...
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1answer
4k views

What is the difference between BRAM and distributed RAM [closed]

I am doing a project on BRAM implementation. What is the difference between Block RAM and Distributed RAM on FPGA in terms of implementation, area, speed etc? Which is better?
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1answer
69 views

How to find a design house with dynamic memory device support? [closed]

I am looking for a design house with dynamic memory device support. Design houses, I found on the web, support only analog, mixed-signal, high-voltage designs and so. I found no design house with ...
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1answer
127 views

DRAM memory organisation

I've been trying to understand the working of DRAM chips but apparently in a lot of confusion. Suppose there are 8 banks in a single chip on a module. Is it only one bit that comes out of a single ...
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1answer
504 views

What determines the ground state of a computers dram?

I have read a paper about the cold-boot attack led by J. Alex Halderman. Full pdf: https://jhalderm.com/pub/papers/coldboot-sec08.pdf The paper shows the decay of a data in memory without power. They ...
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1answer
507 views

FPGA - What is the maximum allowed DRAM capacity on an XUPV5-LX110T Development Board?

I have purchased an XUPV5LX110T FPGA Development board and am unclear as to the size of the DRAM that can be upgraded. Currently I have a SODIMM 256MB that I am looking to increase for the ...
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1answer
520 views

Number of bits Per Column in DRAM

In DDR3, DDR4 DRAM ,I don't get the point that each column gives more than one bits?? Column decoder is also a mux which selects one of the bits in row buffer, and DRAM array is a crossed structure ...
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1answer
1k views

How is a DRAM volatile with capacitors?

There are a few things I understand: DRAM stores each bit of data to a tiny capacitor with some potential difference. Unless the capacitor is connected to low voltage end, the potential difference ...
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3answers
1k views

How can I implement a very simple asynchronous DRAM controller?

I'd like to know how to build a bare bones asynchronous DRAM controller. I have some 30-pin 1MB SIMM 70ns DRAM (1Mx9 with parity) modules that I'd like to use in a homebrew retro computer project. ...
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3answers
712 views

Structure of Larger Memory Modules by using different Size Blocks

I want to design a memory module that includes 2 types of memory cells. I know how to design the memory by using 1 type of memory cells like shown in the picture. But how about designing a memory ...
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2answers
619 views

CAS Latency and static RAM (SRAM)

Every time I read something about RAS e CAS there are mentions to the "DRAM" word. The only difference that comes in mind is the presence of a latch/counter and registers in case of the DRAM. However ...
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2answers
1k views

Using a single transistor & capacitor (DRAM) vs a flip-flop(SRAM) to store a single bit of data

I'm a beginner trying to understand the working of SRAM and DRAM. According to sources, DRAMs use a single transistor along with a capacitor(1T1C) to store a single bit, where the capacitor holds ...

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