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Visitor
Visitor
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Registered: ‎11-11-2020

Digital to Analog (DAC) channels of Spartan 3e

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In Verilog, how to select two DAC channels of Spartan 3e for the output. I have attached, what I have in form of v code.

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Registered: ‎06-21-2017

Write to Input Register A (command = 0000) address = 0000 with one value.  Write to input register B with the other value.  Send the command to update all DACS command = 0001, address = 1111. 

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Teacher
Teacher
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Registered: ‎07-09-2009
A spartan 3 has no DACs on the chip,
so i guess these are on the evaluation board ?
what's the evaluation board ?
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Visitor
Visitor
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Registered: ‎11-11-2020

here is the DAC I am playing with

Untitled.png
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Teacher
Teacher
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Registered: ‎07-09-2009
so you have some sort of evaluation board,
which has some sort of spartan chip on it,
and a LT2624 dac,

so you need to look at the documentation for your board to see how the dac is connected,

Or are you just asking how to select between two signals inside the fpga in Verilog ?

https://www.chipverify.com/verilog/verilog-4to1-mux


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Visitor
Visitor
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Registered: ‎11-11-2020

Yes. Thanks for your reply. But My DAC channels are not MUX type (see fig:untitled2), therefore I can send digital data on them simultaneously but didn't know how to use them simultaneously. So far, I am successful at sending data to one channel by using protocol given below (see fig:untitled3).

Untitled2.png
Untitled3.png
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Teacher
Teacher
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Registered: ‎07-09-2009
As I understand it,
what your asking is about the LTC2624 , and how to use it.

I'd suggest that you are going to get good support from the manufacturer of that chip on their web site.

https://www.analog.com/en/products/ltc2624.html



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Registered: ‎06-21-2017

Looking at the DAC data sheet, you could write to each input register separately, then send the command to update all DACs.

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Visitor
Visitor
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Registered: ‎11-11-2020

may be it is working as MUX, as it allows only one output register to attach to the respective terminal of DAC in the UCF file

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Teacher
Teacher
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Registered: ‎07-09-2009
How many DAC chips do you have ?

We think only one,
The dac chip has multiple DACs in it,
all on the same SPI bus, you only have the 4 SPI signals,

Inside the DAC, there are multiple registers,
at different address's
you use the SPI protocol to select which register you want to address.

To reinforce, the same pins are used for all the transfers.

Read the data sheet for teh DAC chip,
you will see al the registers in there, and how to address them to get the response you want.

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Visitor
Visitor
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Registered: ‎11-11-2020
Ys, there are 4 dac, also we can access each dac by using SPI protocol as mentioned, but at the end you have to assign signal to SPI_MOSI which is connected on FPGA pin T4, therefore can only assign one out of four registers at SPI_MOSI, then at pin T4....?
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Registered: ‎06-21-2017

Write to Input Register A (command = 0000) address = 0000 with one value.  Write to input register B with the other value.  Send the command to update all DACS command = 0001, address = 1111. 

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