Is it possible to generate a 33.3Mhz clock from a 50Mhz clock in VHDL? If so, how?
Many thanks
Danny
Adding to this... with making a PLL in Qsys whats the difference between the "rst" that is always included in the PLL and asynchronous "rst" that is selectable when configuring the PLL?
No. Like Brian said in his comment (actually could be answer) just instantiate a PLL module with 33.3MHz clk output.
Note: your 50MHz and 33.3MHz clocks will now be in different clock domains. So take special care when signals are crossing between them. I would start by googling synchronizer ;)
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I am doing a university project in which i have to build a I2C which have only one slave and will have to transmit a data with 5 bits, 4 bits for the number which is in the range of 0 to 9 and 1 bit to read or write, i'm using a DE10-LITE with VHDL for this project, which has a 50 Mhz default clock, i was looking into the "ALTPLL" inside quartus prime but i can't find the option to set my clock to 100kbps, i did find in the in some forums that the "Set up PLL in LVDS mode" enables that, but for some reason quartus won't let me activate it. My SDA will be 100kbps, and the SCL 50mhz.
As the Other people have said: You don't need a PLL for that. If you already have a default clock of 50MHz then you just need to divide that by 500, using a counter, and then you have your 100kHz clock.
Anyways, you would want to start the counter only when there is a request on the bus. So user16145658 is correct: The generated clock should be the output of your state machine.
You don't need to change the clock of the FPGA, since you are using an FPGA, you only need to implement an i2c core to communicate with the i2c device.
And the i2c specification specifies the rate of i2c
Standard mode (Sm) 100 kbit/s
Fast mode (Fm) 400 kbit/s
Is it possible to generate a 1000 MHz clock from a 100 MHz in VHDL ?
I want to create a 1ns counter and my fpga has a 100 MHz clock!
Clock generation is usually done with Phase Locked Loop (PLL) or Digital Clock Manager (DCM), available in the FPGA as dedicated FPGA hardware resources.
If you want to scale up a clock, like going from 100 MHz to 1000 MHz, then you definitely need to use the dedicated FPGA hardware resources in order to get a stable and manageable implementation.
However, a clock of 1000 MHz is very likely too fast for use in any general logic, like a standard counter. Clocks that fast are typically only used for some very special purposes like internally in a SERDES etc.
So you probably have to consider some different way to implement the required functionality.
I need develope synthesizable custom verilog code for generating a higher frequency clock from low frequency clock i.e from 50 MHz clock i need to generate 100 MHZ clock . kindly help how to do the same.
A pure Verilog solution is not stable, so dedicated FPGA resources must be used.
Please see this previous answer; it applies to Verilog also, even through tagged VHDL.
I need to divide the 50 MHz clock to 1.5 Mhz with 50% duty cycle using VHDL. For that I wanted to use a counter to count the number of 50 Mhz clock pulses until half of the 1.5 Mhz clock period i.e 16.6666 which is in decimal which I don't know how to implement in the code. Can any one please help me with it?
Thank you very much.
I'm not an expert in VHDL but I don't think you can get exactly to 1.5 MHz with synthesizable code. You could maybe get an average of 1.5 MHz if you vary how many clock cycles you wait on the 50 MHz clock until you raise the 1.5 MHz one.
If you only want code that can be simulated then of course you can just use arbitrary delays.
The approach you are suggesting will result in an approximation, which may of course be ok. If not, I would suggest you use instantiate a PLL or clock manager specific to the target technology.
My spartan 3a fpga board has a 50mhz clock while implementing a microblaze with ram ddr2 , it required a frequency of 62mhz which was edited by my program , when asked about this , they told me that 60mhz clock is used to generate other clocks internally but how does a 50mhz clock produce a 62mhz clock which is higher !?
in Xilinx Spartan devices you can use so called DCMs (digital clock managers) that give you a whole lot of possibilities; see Spartan User Guide or Xilinx Spartan 3 DCM. with the synthesizer option, clock multiplication/division is possible.
There are built in technologies that multiply the clock to higher frequencies. See Frequency Multiplier and Phase Locked Loop
under your design name in Implementation window in ISE right click and add new sorce select IPcore then select clocking wizard you can enter the primary freq : 50 mhz and required out freq: 62 mhz and the core generator will do it for you.