Questions tagged [rom]

Read Only Memory - Memory circuits that are only read and not able to be written to. They may have their values stored via mask programmability during manufacturing, or by being programmed at the factory. MEant to contain code or data that is unchangeable, like boot loaders.

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Can I use a 16bit memory with an 8 bit processor?

The address bus is typically a double octet wide (i.e. 16-bit), due to practical and economical considerations. This implies a direct address space of only 64 kB on most 8-bit processors This quote ...
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Chip select for the ROM

An 8 Kbyte ROM with an active low Chip Select input (CS') is to be used in an 8085 microprocessor based system. The ROM should occupy the address range 1000 H to 2FFFH. The address lines are designed ...
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Full adder 2D addressing

I try to implement a full adder circuit using square arrays. I've used Digital software to design it. Also I've tested it. It works fine. But my implementation is quite different from the circuit ...
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46 views

Simple ROM bit cell

I was reading about ROM example from Computation Structures. Here is the ROM example mentioned in the lecture. I set up a simple circuit to understand the inner working logic of the circuit. When I ...
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Understanding Diode ROM

I read that the intersection of a row and column represents a bit, and if an intersection is linked with a diode the corresponding data output line goes low or 0. But why? Take the following figure ...
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What is the pin configuration of an Hitachi HN46532-2 Mask ROM?

I'm working remotely with a person that has a Canon BX-1 computer from around 1978. He has the computer and I have fuzzy memory of the machine. There is no hardware documentation to be found, so we ...
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217 views

How does ROM work? [closed]

ROM is a major part of a computer, and even more so in gaming consoles. How exactly do they work, and how can you make them with logic gates/transistors? I'm currently working on many projects, ...
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230 views

Displaying 6 bit numbers on two 7-segment displays

I designed 6 bit binary adder which should add two numbers in first complement. The numbers are being input via registers. I have to display the numbers and the result on two 7-segment displays via ...
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105 views

Problems with Memory Initialization in Quartus

I have the following code snippet in my VHDL code to initialize a ROM block: ...
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1answer
152 views

Diode ROM with decoder and multiplexers

I have this question on my exam I couldn't answer: A diode ROM has been built using a decoder and multiplexers. If A4A3A2A1A0 = 01001, what is D3D2D1D0? Here is the first schematic: The answer is ...
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75 views

Linker script and data allocation

I know that .data will be in the RAM, but I came across article that says during boot of an micro-controller the initial value of variables is stored in the ROM and ...
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130 views

How is an EEPROM different from a Flash memory? [duplicate]

I am trying to understand the terminology used for various non-volatile memory chips for example as EEPROM and Flash. Is there any preference to use the word EEPROM or Flash for specific type of ...
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107 views

If ROM has no data inputs, how is it able to produce data outputs?

I've been reading CODE by Charles Petzold, and he mentions that ROM has no data inputs, only data outputs. How does ROM know what address signals to recieve then, if there is factually no data ...
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Find ROM and RAM in .bin file for micro controller

I use the Arduino IDE to compile some code to a 32-bit ARM Cortex-M3 based microcontroller. The result of the compilation is <...
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61 views

How do I produce WE in this diagram?

I have designed a memory system that has 10KB ROM followed by 6KB of RAM. The ROM begins at 0000H. I had to use two 4K x 8bit ROMs and one 2K x 8 bit ROM. I also have to use one 2K x 8bit RAM and a 4K ...
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52 views

Chaging EA/VPP by software on Intel MCS-51/8051

I'm designing a circuit that uses the combined Program/Data bus from Intel MSC-51 as advantage. By the MCS-51 specification it has an internal 4K ROM and a EA/VPP pin that if set to high will access ...
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Core rope rom not working

I am trying to make my own core rope rom, according to the link. I have 15mm ferrite cores, which I wound about 30 times with 1mm magnet wire. I thread the primary ( also 1mm wire) through one of ...
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Why don't the fuse connections in programmable ROM cause the whole matrix to be shorted together?

If the rationale of using diodes in ROM (rather than simple wires) is to prevent the matrix being shorted together, then why does shorting not occur for programmable ROM - which has blowable fuse ...
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Why is one of the transistors in ROM sense amplifier twice the width of the one opposite of him?

The picture is of Sense Amp design of ROM component in which a 'dummy' bit line is used to imitate the current so that the proper information can be derived from the memory cell by comparing the ...
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Combining two schematics of 1kx3 NOR MOS PROM components into a 2kx6 PROM component

Today after class we were left with an exercise of creating schematics and combining two components we learned about today. The exercise is to combine two 1kx3 NOR MOS PROM components into a 2kx6 PROM ...
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ROM initialization in VHDL for waveform generator

I have to create a waveform generator and i used matlab to generate the sine wave. Now my TA told me to store the points from the wave in a ".mem" file then initialize the ROM by i guess importing ...
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Finite State Machine FSM

I understand how to make state diagram and make combinational logic (gates) to get a boolean equation for the next state bits and the output bit, but what is the function of ROM here ?
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Two bits per ROM cell

Modern flash memory uses multiple voltage levels to cram two or more bits into each cell, in order to increase density. This technique is not used in DRAM (perhaps because it would compromise speed?) ...
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116 views

How to store a const string at a memory location in Microcontroller?

I have two questions ...
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Why isn't the BIOS' ROM chip made using CMOS technology?

After reading a computer hardware course on BIOS/CMOS, I'm still unable to determine the reason why the BIOS' ROM chip isn't built using CMOS technology, and why it is connected to a separate chip ...
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489 views

What to call the cells of memory in a computer or a microcontroller?

I don't know if this is the right forum to post this question, but I thought so because this forum is for educators and I'm a trainer and my question is related to education. I want to do an ...
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Why address bus bit and data bus bit different [closed]

Recently I read address bus is 16 and 4 bit data/address in ROM.
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How to write a program for 4-Bit CPU made in Logisim?

So I finally got my 4-Bit CPU working on Logisim, and am trying to get it to do commands and display them, but am unable to do so. My CPU looks like the following: I am trying to implement the ...
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How is normal ROM programmed [closed]

Perhaps this question may sound silly,and am sorry if there are similar questions answered already because i couldn't find one, as per guidelines. Mask ROM(MROM) are programmed while manufacturing,...
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4answers
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Pull-up or pull-down when building an LED ROM for 74HC logic levels?

I want to build a LED ROM (a diode-ROM, but using LEDs). The LEDs will be driven from the outputs of a 74HC138 or similar. They will drop 1.6 - 1.7 V (red). The ROM will have eight words of ...
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807 views

.BIN file for ROM IC using proteus

Trying to load a .bin file into a 2732 ROM chip in Proteus. Having trouble finding the exact layout of code I need for the .BIN file. So far i have tried writing the following in notepad and saving ...
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380 views

What does the square brackets mean?

In this diagram: What does the S[2:0] mean? I think it is the state but why is the state in 3 bits? What does the 2 and 0 mean? Cheers!
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Associating ROMs and RAMs

Can someone explain to me how to associate smaller RAMs and ROMs to make a bigger one? For example: How do I make a 1024x8 RAM with 512x4 RAM?
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Were mask ROMs with stock contents ever sold? or why not?

To clarify: did any of the mask ROM or discrete IC vendors make and sell ROMS (or effective ROMs optimized by giant Karnaugh map) with fixed non-proprietary contents that could be used in building a ...
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185 views

Increase EEPROM capacity and data lines

Question: I need to increase the capacity and data lines of a EEPROM board using decoder and/or basic logic gates. The EEPROM is Hitachi HN58C1001. it is 128K by 8 bits. Task is to make it 1M by 32 ...
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176 views

Where does character pointer resides in memory, ROM or RAM? [closed]

I am running Embedded C on some ARM Cortex-M4 target which facilitates with both ROM and RAM support. I have a character pointer in my code: char *temp = ""; ...
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125 views

How to generate an enable signal when a bus value is in a very small range?

I am trying to build an MC68010 single-board system, and the first four 16-bit words (I am treating it as a 23-bit word-addressed system) of memory need to read a constant value (00100000h 00007C00h) ...
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260 views

IS it posible to emulate firmware? [closed]

Currently, i've been trying to work on virtualizing a motherboard from an old Lucent BZ5000 equipment, my idea is to emulate the BIOS from that equipment on a modern PC and be able to connect ...
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225 views

Determining the ROM contents of a circuit

I have a state transition table and a truth table stored in a ROM. The truth table was obtained from the state transition table but I'm not sure how. Could anyone explain how the truth table is ...
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1answer
403 views

Density of ROM vs Flash

Let's say I had a very large static dataset that I'd like to distribute via solid state memory to a lot of people. Let's say it's on the order of terabytes. What would be the densest type of storage I ...
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Memory interfacing with 8086

The 8086 microprocessor can address up to 1MB of memory (20 bit address bus). Most books show a diagram of this 1MB memory which in turn shows interrupt vector tables, DOS function, BIOS routines ...
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145 views

How to build a larger ROM using smaller parts?

How can i build a 1024-bit ROM using 512-bit and smaller ROM's? Is it good idea to use a 2:1 MUX and that selects on of 2 512-bit ROM's?
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Flash/obtain ROM code for Sitara on BeagleBone Black

How is the ROM code loaded/provided on the BeagleBone Black? I see a few possibilities: It is loaded on in TI's factory and is immutable [unlikely] It is flashed on during manufacture of BeagleBone [...
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Pic micro controller

i am programming pic microcontroller using mikro c , i want to store array of 8 bit samples generated from audacity (it's a software used to generate header file from audio file) , i got one header ...
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4k views

How does Option ROM work?

(Excuse me if this is not the appropriate place for such question. I just moved it from StackOverflow.) I just read the wiki article about Option ROM. A few questions I'd like to ask: Is Option ...
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1answer
365 views

STM32F0 Crashes from literal string declaration

I literally feel like I'm going crazy! I'm trying to write an exceptionally simple program that can request a list of local WiFi networks using an ESP8266 and the AT+CWLAP command. The issue doesn't ...
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663 views

Hierarchical memory organization

I get everything about this picture perfectly clear, but what I don't understand is where is ROM located? Isn't ROM part of BIOS? Where do we sort BIOS in this memory organization?
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116 views

Way to read CMOS 4-bit computer?

I have a board I am trying to debug and it has a Mitsubishi 4-bit CMOS computer on it of type M34225M2-163SP: http://pdfs.datasheetdirect.com/view/2994013/M34225M2-XXXSP.png I assume the ...
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Positive Edge Triggered D-FF by switches

if Given that this circuit implements Positive Edge Triggered D-FF so What is the purpose of the switches S2 and S4? Hwo can i know what is the kind of S2 and what is the kind of S4 (P or N)?
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Do different address spaces exist for RAM and ROM in a typical microcontroller? [closed]

If a microcontroller has 16 bit address space from 0000H to FFFFH, will the RAM, I/O registers, memory mapped I/O and ROM(Flash/EEPROM) share the same address space linearly, or will there be a ...