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Questions tagged [memory]

Consider instead more specific tags, e.g., dram, sram, flash

65
votes
11answers
8k views

How can anyone use a microcontroller which has only 384 bytes of program memory?

For instance a PIC10F200T Virtually any code you write will be larger than that, unless it is a single purpose chip. Is there any way to load more program memory from external storage or something? I'...
53
votes
10answers
24k views

Why is RAM not put on the CPU chip?

Modern CPUs are very fast compared to all things external, including memory (RAM). It is understandable, since CPU clock frequency has reached a point where it takes several clock ticks for an ...
38
votes
8answers
19k views

Why do microcontrollers have so little RAM?

Maybe this is more of a perceptional problem, but it seems like microcontrollers have advanced by leaps and bounds in the last 20 years, in almost all regards, higher clock speed, more peripherals, ...
24
votes
3answers
12k views

What resides in the different memory types of a microcontroller?

There are different memory segments to which various types of data are put into from C code after compilation. I.e: .text, .data,...
24
votes
1answer
3k views

Why does flash memory have a lifespan?

I've read that flash memories can "only" be reprogrammed 100000 to 1000000 times, until the memory storage "deteriorates" Why exactly does this happen with flash and not other memory types, and what ...
24
votes
6answers
6k views

What is a flip flop?

There seem to be a number of different definitions of flip-flops and latches out there, some of which are contradictory. The Computer Science text book for the course I teach is probably the most ...
23
votes
4answers
10k views

How do you determine how much flash/RAM you need for a microcontroller?

Let's say you are starting an embedded project with some known functionality. When you select a microcontroller how do you select how much RAM you need? Do you use a developer board and code your ...
20
votes
7answers
10k views

Is it possible to use multi gigabyte DRAM modules with a microcontroller?

I have two leftover 2GB RAM modules that I removed from my MacBook Pro when doing an upgrade. I was just wondering if these were usable with, for example, an Arduino. I'd be too much of a beginner to ...
20
votes
3answers
3k views

SRAM isn't blank on powerup, is this normal?

I had finally finished my Z80 memory board, but I was disappointed to see that it wasn't working properly (simple NOP test with the address lines connected to some LEDs) as the counter quickly ...
18
votes
7answers
5k views

Why is serial EEPROM preferred over parallel EEPROM?

In the wikipedia page for EEPROM: http://en.wikipedia.org/wiki/EEPROM it is given that "Parallel EEPROM devices typically have an 8-bit data bus and an address bus wide enough to cover the complete ...
16
votes
2answers
2k views

Parallel RAM without large number of pins?

Back in the 1970s, Texas Instruments had a now-discontinued range of products that they called GRAM (and read only equivalent GROM) which was basically a standard memory chip with address and data all ...
14
votes
4answers
13k views

Why is L1 cache faster than L2 cache?

I'm trying to understand why certain CPU cache memories are faster than others. When comparing cache memory to something like main memory, there are differences in memory type (SRAM vs DRAM), and ...
13
votes
4answers
9k views

Does a USB mouse have memory that could be used to store malware?

I worry that this might get flagged as too broad, but here it goes: Lately I've been thinking about the possibility of loading data on peripheral devices. One of the most used peripherals is the ...
12
votes
4answers
3k views

What happens when microcontrollers run out of RAM?

It may just be a coincidence but I've noticed the microcontrollers I've used rebooted when they ran out of RAM (Atmega 328 if hardware specific). Is that what microcontrollers do when they run out of ...
12
votes
7answers
7k views

Saving data to an SD card memory module using an Arduino

Is it possible to save data from the Arduino to an SD card memory module?
12
votes
4answers
17k views

What is a good choice for an ARM to interface with external memory?

I just completed a project using the LPC2132 chip, but ran into problems with using up the whole 64kb of RAM. For my next project, I'd like to use something that can reference an external, much ...
12
votes
3answers
7k views

What are the implications of using PROGMEM?

With large amounts of text variables, I've found it necessary to store them in the Flash memory using PROGMEM. What are the positive and negative consequences of storing large variables in Flash (...
12
votes
2answers
4k views

Are page table walks cached?

On a microprocessor with hardware TLB management (say an Intel x86-64) if a TLB miss occurs and the processor is walking the page table, are these (off-chip) memory accesses going through the cache ...
11
votes
2answers
1k views

Inbuilt flash memory size not enough

I am using TM4C1230C3PMI controller from Texas instrument in one of my project. It has 32KB of internal flash, which is not sufficient for my application. Higher flash sized micro-controller are ...
11
votes
2answers
22k views

Flash and EEPROM

Atmega16 datasheet says that it has a) 16 Kbytes of In-System Self-programmable Flash program memory and b) 512 Bytes EEPROM. Can a microcontoller have two separate ROMs which can be programmed ...
11
votes
3answers
2k views

SDRAM Prototype vs Production Woes

I have a design using an LPC1788 together with a SDRAM module from ISSI (IS42S32800D). This is a 32bit interface. I have routed this design out and had a prototype made with a PCB manufacturer that ...
11
votes
5answers
6k views

How can one make an analog voltage memory circuit?

I am looking for a circuit that can, on input, remember a certain voltage and output that voltage indefinitely even after the input has been taken away. The circuit should not change its output until ...
11
votes
5answers
3k views

memory for the simplest possible computer (Pi0K)

I'd like to build the simplest possible computer. I don't care about speed or storage, indeed having slow speed and low storage is a huge advantage as I want to build it out of transistors (ideally ...
10
votes
10answers
11k views

How to make 1 bit permanent memory circuit?

I would like to make a simple circuit to store or save 1 bit of data. The circuit should be able to remember the state of an LED ( on or off ) even if the supply is disconnected from the circuit. I ...
10
votes
7answers
12k views

Use of malloc in PIC

How can I use malloc() and free() functions in a PIC? I've checked the stdlib.h header and ...
10
votes
6answers
11k views

DIY USB Mass Storage Tutorial

I was just wondering if there was a tutorial anywhere on how to make your own USB Flash Drive and I don't mean take apart a USB and put the guts into something else, I mean put together the flash ...
10
votes
2answers
8k views

MSP430 Code Size in CCS

This should be pretty straight forward, but my google-ing is not turning anything up... I can build my project successfully in TI Code Composer Studio (CCSv5) and target my device. Now I want to ...
10
votes
3answers
4k views

Why must flash memory be written/erased in pages/blocks?

Title says it all. I'm trying to understand the workings of flash memory technologies, at the transistor level. After quite some research, I got good intuitions about floating-gate transistors, and ...
10
votes
3answers
4k views

Reading a Micron 29F32G08QAA NAND Flash IC

It would be nice if this was a shopping question - but it is 99%+ likely to be an electronic construction question :-(. I wish to find the quickest / easiest / cheapest way to read a 4GB NAND Flash ...
10
votes
1answer
2k views

FPGA link to external memory

I am trying to use the cellular ram on the Nexys 4 FPGA development board. I am using Xilinx Vivado and would like a Microblaze soft core processor to be able to perform reads and writes. So far I ...
9
votes
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 ...
9
votes
3answers
946 views

Can you run an x86 class processor ramless?

Modern x86 processors have at least 512K of L2 cache. There are applications which would fit entirely into this amount of memory. Can you run these chips with no RAM attached? If so, is there a way to ...
9
votes
5answers
2k views

Memory suggestions for MSP430

I'm developing a measurement application with the TI MSP430 and I would like to hear some suggestions on what type of memory I can use. The idea is to use it for logging during a certain time and ...
9
votes
3answers
5k views

How does random memory access of RAM work?

HDD works in a partly sequential manner. However, RAM is known for random memory access, allowing equal speed of memory access for every location at every time. So, what makes RAM so special? How ...
9
votes
1answer
8k views

What's the usage of the three boot mode of STM32f103?

If you see in refrence manual of STM32f103, you can see three boot mode for it. well, What's the usage of the three boot mode? please say to me by example for each mode.
9
votes
2answers
1k views

Need some help understanding PIC memory map

Some background. I use MPLABx with a PicKit2 to program different types of pics. At the moment its the 16F887. I try to stick to the Hi-Tech PICC Lite tool chain but I'm growing increasingly unhappy ...
9
votes
1answer
1k views

Freezing DRAM for forensics (coldboot)

I've known about the coldboot trick for a while, but have never really considered the physics behind it. I've read the paper, but it doesn't really cover why it works. How does physically cooling a ...
8
votes
9answers
1k views

EEPROM with high endurance

I am currently working on one embedded project in which I have one counter which will be active all the time. If the power goes down then also I have to store last counter status and load it back in ...
8
votes
3answers
6k views

What is flash memory wait states?

I'm using a freescale PowerPC microcontroller. In the flash memory module in the datasheet, the number of "wait states of the flash memory access" is configurable. The following is the part of the ...
8
votes
5answers
4k views

SRAM which two chips can read/write

I'm looking for a small, 32KB or so SRAM device that two MCUs can read or write (at two different times; I don't need simultaneous reading/writing.) It would be good if it used a serial interface as ...
8
votes
3answers
512 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. ...
7
votes
9answers
6k views

Microprocessors/Microcontrollers - Do registers have addresses?

My Embedded Systems professor keeps referring to the memory locations of registers as their respective "addresses". I'm confused by this; I was always under the impression that in any microprocessor, ...
7
votes
4answers
1k views

Method or function to determine if pointer is to address in flash or RAM?

I'm working with an ARM Cortex M4 microcontroller that has a DMA, or peripheral DMA controller. One requirement of the DMA is that it cannot access pointers to addresses that exist in flash, but only ...
7
votes
6answers
3k views

Exploiting stack buffer overflows on an Arduino

Is it possible exploit stack buffer overflows on an Arduino board?
7
votes
1answer
2k views

How does memory wear out?

I know that after time due to writing/re-writing memory wears out, and I was reading about a microcontroller from TI which uses "wear leveling" to insure the longest life of some EEPROM that the chip ...
7
votes
2answers
8k views

Checking memory footprint in Arduino

I'm working on a simple project with my Arduino. Recently I had to convert one of my variables to a long instead of an int, and in order to keep things simple I just moved over all the numbers that it ...
7
votes
3answers
4k views

DDR1 Layout Considerations - DOs and DONTs

I am novice to high speed design. Before getting in to DDR, I recently learned about impedance matching and how it is done, likewise I learned about length matching and how it is done.(Baby steps ...
7
votes
1answer
485 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 ...
7
votes
1answer
26k views

Meaning of control pins: CE, OE, WE

Just understanding some syntax. On my Ram (6116) and Rom (27C64) it has a asserted low CE and OE pins. These I believe are control pins. I'm assuming to use the RAM for example, chip enable (CE) has ...
7
votes
2answers
3k views

How to implement memory mapped IO

I am describing a system in VHDL. This system already contains a processor, a DDR SDRAM controller and a VGA controller. VGA reads pixels from SDRAM (already validated and proven in FPGA). Although ...