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Martin1234
Senior
Joined: Jan 27, 2004
Posts: 110
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 Posted: Wed Dec 21, 2011 4:58 pm Post subject: VMM clocking blocks and non-blocking assignments |
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I am looking at the following code example from the VMM user guide:
| Code: |
foreach (bytes[i]) begin
...
@(this.sigs.mtx);
this.sigs.mtx.txd <= nibble;
...
end
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If I want to debug something like this in the logfile, I will add `vmm_debug "statements":
| Code: |
foreach (bytes[i]) begin
...
@(this.sigs.mtx);
`vmm_debug(log,"Driving %0h",nibble);
this.sigs.mtx.txd <= nibble;
...
end
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It looks like the timestamp in the logfile and time of the actual application of the value on the signal will be off by one clock cycle. Am I seeing this correctly? |
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Tejasaurus
Newbie
Joined: Mar 07, 2012
Posts: 4
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| Posted: Thu Mar 08, 2012 1:22 am Post subject: |
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| Interesting. So if the `vmm_debug statement is executed at system-clock time 't', you saying that this.sigs.mtx.txd gets assigned at system-clock time 't+1'? Does the waveforms say this? |
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dave_59
Senior
Joined: Jun 22, 2004
Posts: 974
Location: Fremont, CA
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| Posted: Thu Mar 08, 2012 10:29 am Post subject: |
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Assuming mtx is the name of a clocking block, | Code: | | this.sigs.mtx.txd <= nibble; |
is not a non-blocking assignment. It is a clocking block synchronous drive. The actual application of the assignment is defined by the clocking block. |
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