Error physical type

[pauleric]

Hi

I am running a simple code which includes time data types. I am encountering this unknown error. Could you tell me what this error message means ?

The error message:
Type definition is not authorized : 'PhysicalType'.

I m a beginner in this language, so if you can help me...

Thanks for your time

pauleric

 

[Iamjonscranium]

please post your code if you could. what comes to mind is that maybe you activated something as, for example, a bit value, but later stated it as an integer. i am a biginner also, but i believe i've seen this error. so if you post some code i may be able to help further.

 

[jeandelfrigo]

Pauleric,

If you are trying to use a time data type for actual synthesis of your code, this means generating a bitfile or hexfile to download in your PLD or FPGA, this error is very logical.

A synthesis tool does not know how to implement this.

For example :

A statement like "wait for 10 ns;" is perfectly usable in code that you want to simulate, but if you want to implement this, it will not work. For the simple reason that the device, be it an FPGA or a CPLD or whatever has no idea what a ns or us or s is. A programable device has no built in timebase. If you want one you need to implement it.

The only notion it has of time is when you use a clock signal. The period of the clock is the timebase.

for example :

You use a 100 MHz clock, this is 10 ns period.
You want to wait for 70 ns, so you will need to wait 7 clockcycles and you will need to either use a counter or a clockdivider (this is actually the same thing).

I cannot say with absolute certainty that there are no high level synthesis tools that will do this "translation" for you, but I would not advise you to let them do it, if they exist in the first place that is.

Sorry for this limitation but VHDL is for hardware

regards

jeandelfrigo