Questions tagged [register]

A special, high-speed storage area within the CPU.

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1answer
110 views

What parts/sections of a CPU take the biggest number of transistors?

I was surprised to hear CPUs only have a number of ALUs. What are most of the transistors in a CPU dedicated to?
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1answer
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Not getting correct results displayed from register

I am trying to input the numbers 1,0,3,2,32'hFFFFFFFF,32'h00000001 into the registers 0,1,2,3,6, and 7 respectively. I am doing this through always @(posedge clk) ...
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37 views

How to instantiate module with variables

I declared alu_result as a reg because I need it to be a variable data type for my case statement. But when i do this, I cannot pass it my ...
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32 views

How to cascade IC 74HC161 correctly?

Currently I have this 4 bit CPU as shown in the schematic diagram below. What I wish to achieve: Add one more output register to make the CPU output a total of 8 bits Show alphabet using the 8 bits ...
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2answers
54 views

How can I convert data from a sensor register to a float value?

Can anyone please help me understand how I can convert data from a sensor register to a float value? Say I am reading the sensor register as following: ...
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2answers
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Flip-flop vs latch: Do flip-flops have an edge detector integrated?

As far as I know, a latch and a flip-flop are the same excepting that flip-flop only "works" with an edge of the clock (let's supose rising edge for the question.) To make the flip-flop &...
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3answers
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Physical size of the registers for x86

We have an 8-bit register called CL on x86 CPU architecture. Does it mean that physically it contain 32 bits, but we have access only to lower 8 bits? Or does ...
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1answer
100 views

Why any modern CPU masks 5 lower bits in a CL register for shifting operations

I'm digging into left and right shift operations in ASM. From IA-32 Intel Architecture Software Developer’s Manual 3 All IA-32 processors (starting with the Intel 286 processor) do mask the ...
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1answer
57 views

How do I use a 4-bit Adder, 4-1 MUX, and 2-1 MUX to implement various micro-operations on registers?

One of the exercises in my Logic Design coursebook requires me to create a circuit that handles following micro-operations on 4-bit registers R1 and R2. R1 + R2 R1 - R2 R2 – R1 R1 – 1 -(R1 + 1) 0 -1 ...
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Vivado is not properly gating my registers?

I have a register which holds 12 bits written in VHDL within Vivado which is not being gated properly. The code is very simple, and is as follows: ...
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2answers
46 views

Is it possible to have a register with multiple drivers?

This is just a theoretical question I have. Imagine we have a register (a reg signal in Verilog for example) and two possible inputs that have to write to that register. I am assuming all signals are ...
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1answer
124 views

What happens when a program needs to use more than the allotted 16 registers?

I'm just learning about how programs work under the hood of a computer. We discussed how registers are a limited resource to the CPU. So what happens when a program is massive and needs more than 16 ...
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MOV C, B instruction in 8085 takes 4T cycles so when and how does the data copies from B to C

As specified all over the internet, MOV C, B instruction in 8085 only takes 4T states to execute but the opcode fetch and decode take 4T states, which means the transfer of data from one register to ...
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2answers
58 views

SN74LS245N outputs 1 Volt when OE is high, 0 Volts when OE is low

We have been making a Register. When we write all ones, it works fine. When we enable it back onto the bus using 74LS245, it doesn't enable. We used our Multimeter to measure the volts. It seems to ...
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1answer
34 views

Guidance on programming control registers in a device (DAC)?

I need to program audio DAC chip registers, I know it is controlled through I2C pins but other than that im clueless. DAC is Ak4493 First off what options are there of devices to control it? e.g are ...
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3answers
132 views

How can a 4-bit CPU have 40 instructions?

Currently, I am using Logisim(yes, still Logisim) to build a 4-bit variant of the 8-bit SAP-1 microcomputer. However, I ran into a problem with the instruction register. Let me explain. The SAP-1 has ...
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1answer
47 views

Setting HSYNC and VSYNC registers

I am using the FT801 (datasheet) to drive a Newhaven 4.3" TFT display (datasheet). The TFT datasheet specifies the normal timing parameters (hsync/vsync peroid, front porch, back porch) on page 6. ...
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1answer
87 views

What exactly is a register?

Sometimes I'll look at registers in asm or when debugging a C output. What exactly is a register? In my understanding, it seems like it would consist of, for example 16 D-type flip-flops connected to ...
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2answers
81 views

The CPU has registers, but doesn't the RAM have registers too?

At low-level, registers are the same as a bunch of flip-flops connected by the same clock, so I would think RAM is made of registers. I've been reading, though, that registers are only in the cpu, ...
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1answer
76 views

Stack error when jumping from bootloader to application

I have been trying to jump from my bootloader to an application for a while now but I can not figure out what is going wrong. I am hoping someone here might be able to help me. I am using Texas ...
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0answers
54 views

Imprecise bus error when setting Vector Table Offset Register. TI CC2652

I am developing a bootloader and want to jump to the application. I am new to this so I am not entirely sure I am doing it right, but as far as I know I have to change the value stored in the VTOR (...
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1answer
46 views

Decoder inputs needed given 32 registers

I have a couple of questions about decoders. My first is this: If I have a register bank with 32 registers, how many inputs are needed for the decoder and why? I think that you need 5 inputs for this ...
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3answers
85 views

Is a typical register rising edge or falling edge? [closed]

I'm using Logisim to build a 1-bit CPU. However, I am having issues with timing the registers up with the clock. In a CPU, should registers be rising edge or falling edge? Or, could they be something ...
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1answer
70 views

Problem with setting usart by registers

This is the code. I'm using stm32f103c8t6 and I want to communicate with a Bluetooth module (Hc-05). I'm new with STM and I'm using registers and want to send just 65 for a test but it doesn't work ...
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0answers
35 views

How to access Realtek SMI interface without a dedicated processor?

I'm working with Realtek's RTL8367 switch IC. Background: I am having trouble with throughput being unbalanced. If I run iperf between two ports in one direction I get a different throughput if I ...
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2answers
103 views

Generating 40 kHz square wave using ATtiny13

I'm using an ATtiny13 running at 1.2 MHz and would like to generate a 40 kHz square wave on PB3 and PB4. The signal on PB4 should be 180 degrees offset (inverted) from PB3. I know that I need to set ...
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1answer
77 views

How to enable the DMP of the MPU9250?

The datasheet mentions some Advanced Hardware Features which gets executed by the Digital Motion Processor. I'd like to use the ...
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4answers
4k views

Where are registers and what do they look like?

I racked my brain through my comp-arch class and reread wiki’s article on hardware registers (they’re flip-flops, I get that), but one year later and I still don’t understand what a register ...
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2answers
164 views

Why would this cause a latch?

I'm reading ZipCPU's tutorial and got confused. Specifically, I'm referring to this page. To transcribe the Verilog code: ...
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1answer
127 views

The error “requires SystemVerilog extensions” while declaring an error

What's wrong with the following code? The array "FIFO" is declared correctly, but an error appears. Can you please help how to fix this? ...
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1answer
98 views

Question about 74LS164 8-bit serial in parallel out shift register

With the 74LS164 8 bit parallel out serial shift registers, I'm confused about a few things. In the datasheet (page3) on the logic diagram why do they suggest using an active low inverter before the ...
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1answer
50 views

How does a number is saved in a register

I've tried looking online, but I still haven't quite figured it out - does a number, for example 0x100 saved in a register by some convention like little/big endian like thigs are saved in memory or ...
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2answers
109 views

SN74HC595N Shift register output bizare

simulate this circuit – Schematic created using CircuitLab I'm using an 8-bit shift register on a very basic application for learning purposes, I have three buttons connected to SER, RCLK & ...
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0answers
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Do these two memory register diagrams look correct?

So to start this off I have used J-K flip flops instead of D flip flops due to the equipment that I'll be using (Logic Tutor LT345 Mk2). The first diagram I am confident is correct but the 2nd diagram ...
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Why did they make the 74x170 (670) register file asychronous, no CLK input?

I am designing a retro computer as a project to learn digital electronics hands-on (not FPGA programming). I currently have an accumulator machine similar to the PDP-8 where the ALU has the ...
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1answer
71 views

Are Tri-state buffers even necessary?

I'm trying to make a 1-bit computer, and I'm stuck on the registers. I think I am going to have 2 of them, and I want a way to separate their outputs. Let me explain. Let's say Register A has a 0, and ...
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1answer
123 views

how to copy the value of a register into another (Logisim)

how to design the circuit that copy the value of register into the other? I only know the register can be written or loaded, but how is it possible that after loaded the value of 1 register and still ...
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1answer
262 views

Register File for MIPS Processor

I am writing code for Register file (32 registers, each of 32 bit) for MIPS Single Cycle processor. I want writing to happen at the negative edge of the clock. As usual, reading can happen any time (...
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1answer
143 views

Initial value for 32 bit register made using D F/F in verilog

I am trying to make a 32-bit register using 32 negative edge trigerred D F/F. Here is the verilog code for D F/F: ...
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1answer
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104 views

Verilog: Register File assignment not updating on clock pulse

I wrote some fairly simple code in Verilog to implement a 32-bit deep, 8-bit wide register file. However, when I actually run a behavioral simulation of the thing the two data-read lines (rd0_data and ...
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1answer
170 views

Do I really need to learn how to use registers - Programming a microcontroller? [closed]

I have a curious question. Do I really need to learn how to use registers when I program a microcontroller? I have been using Arduino for a long time. I quit using Arduino and starting to use STM32 ...
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How to set registers of accelerometer BMA220?

I first wrote my problem in Arduino Stack exchange (https://arduino.stackexchange.com/questions/68438/how-to-manage-interrupt-from-accelerometer-bma220) but I was told that I might get a better help ...
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2answers
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“Increase” of a register in VHDL and hardware synthesis

Suppose you have already defined a register (for instance called "reg") in VHDL, for instance as a vectors of 4 bit. Now consider the operation: reg <= reg + 0001; it is like reg ++ in C. My ...
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How to use two Demux to index a matrix layout of registers

Consider the following. Let's say for simplicity sake I have an arrangement of 8 bit registers in a 4x4 matrix layout. I could easily use a Demux that has a 4 bit input select line for the addresses ...
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1answer
96 views

NVIC memory map ARM cortex M3 STM32f103

I do not understand the following memory map regarding the NVIC registers in Programming Manual for STM32f103 page 129. It says that the offset address for NVIC_IPR0 is 0x300 and that of NVIC_IPR20 is ...
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2answers
272 views

How can I transform the code for a read-write register to a read only register in Verilog?

I have the code for read write register here ...
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1answer
149 views

How to specify a value for each bit of the reg in Verilog?

I want to declare a reg of 8 bits and set the value for each one of the bits separately (based on another "counter" reg) inside ...
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1answer
40 views

Verilog Reg File: Cant mix blocking and non-blocking assigment

I want to implement a blocking read to read the data as soon as it is written. I am trying to implement a MIPS 1 pipeline and i need the data to be available in the same clock it is written. The flips ...
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2answers
84 views

Writing to registers on I2C device

I'm currently working on a side project which uses an SSD1306 128x64 OLED display. I'm then using I2C to communicate to this. However, I'd like to better understand what exactly is going on when I'm ...

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