Hot answers tagged

12

Word-wide memory is addressed with a single address bus. When a word is read from an odd address, one byte is in one word, the other byte in another. You cannot address both bytes at the same time. Even if the memory had a separate address bus for each byte, the processor does not have the pins to address both address busses at the same time.


8

The book is slightly wrong, but let's try to clear it up. The thing is, you can put 125 on the address bus. But you cannot read addresses 125 and 126 in a single clock by doing so. Basically this is because the numbers 125 and 126 differ in bits other than the last bit. The 8086 has 20 address lines (A19:A0) and 16 data lines (D15:D0). Actually the 16 data ...


4

The devices are not "daisy chained" in an I2C setup. The total number of devices depends on the capacitive load on the bus. Each device, and it's associated traces, add capacitive load. Look at your devices datasheets for how much load each device will tolerate. You'll have to do some math and know something about your PCB layout if you really wanna ...


4

In fact the 8086 does it exactly the latter way you describe, and it has to use two memory cycles to do it. To access word from address 125, the CPU puts 125 on the address bus. Since it is an odd address and only high byte is needed from this address, address A0 bit will be 1 and BHE is active, so only high byte of memory responds. Next, the address 126 is ...


3

From what I understand, there is a clock in a micro-controller, and every little task is executed at a clock pulse. At least one clock. Modern microcontrollers may have more than one, and numerous clocks derived from the one master clock. Question: Can two or more actions be performed simultaneously (In the same clock pulse) ? Can they? Yes. Are they?...


2

I2C and SPI are limited by capacitance, to this end you can trade off speed for distance if needed, SPI also has a secondary limitation at higher data rates of length, as signals can only travel through the copper so fast with I2C assuming a 100KHz bus, the recommendation is 400pF, this can be made up of the "load" of the device, which is generally very low,...


2

It doesn't. There are other dedicated circuits that process (amplify and demodulate/digitize) the signal from the antenna, and the results are presented to the CPU at a rate that it can handle. There are some chips that have this RF circuitry integrated onto the same die as the CPU. For example, in the ESP32 block diagram, the CPU is in the orange block in ...


1

You have misread the schematic which you linked. The part you have circled is actually U2, the debug interface comprised of an additional MCU, with its own clock circuit, while U1 is the target MCU placed in diagonal orientation in the middle which runs your program. While some similar boards save a little money by feeding a clock output from the debug MCU ...


1

The processor you circled is part of the debugging interface. It is not the processor that you can program. The processor that you can program is the one shown below, mounted at an angle. The debug processor implements the USB interface for this Launchpad board, so changing its clock frequency is likely to break the USB communications.


1

The always @(posedge clk) statement is actually a combination of two statements: The always procedural block: always ... begin //Body of 'always' block end And a sensitivity list: @(posedge clk) - At the positive edge of clk @(signal or signal) - Any change in listed signals @* - Any change to any signal used as an input to the ...


1

You must have picked a piece of equipment labeled as 'No Simulation model. Now, if you place this component in your circuit, then there will be an error named - "No model specified for ... " Here 'No model specified for U1:A' means that the IC named U1:A is not approved for simulation. You need to replace it with active component. So you ...


1

Consider this: - I've highlighted the clock frequency in green. For the standard setting, the clock frequency can be no greater than 100 kHz but there's no reason why you can't operate it a 1 nano hertz. If operating at 1 nano hertz then the low period of the SCL clock could be as long as 500,000,000 seconds. But who really cares because what this data ...


1

The two most common speeds in I2C are 100kHz (standard) and 400kHz (fast). There are higher speeds in the specification but these are the two most commonly used. It is not necessary to actually use those speeds; in normal mode there is no reason that we could not use a 50kHz clock (100kHz is the maximum speed in normal mode and for this reason it is ...


1

I have now returned to this project of mine, I have finally realised my silly mistake. According to the typical connection diagram there should be a 5.1Ω resistor between VA and VD pins, but I accidentally originally put a 5.1kΩ resistor there. After replacing the resistor with the correct one the ADC works all right.


Only top voted, non community-wiki answers of a minimum length are eligible