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Simulators >> Circuit Simulators >> Verilog AMS netlisting and three terminal devices
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Message started by aznaragorn on Jul 7^th, 2004, 1:43pm

Title: Verilog AMS netlisting and three terminal devices
Post by aznaragorn on Jul 7^th, 2004, 1:43pm

I want to extract Verilog AMS netlists of past schematics to simulate in the AMS environment. However, I am hitting a roadblock because of three terminal devices I have used in my schematic. I want the object propery "bn" (bulk node connection) in my schematics to specify the fourth connections for these 3 terminal devices. For spectre and hspice netlists, the CDF used progn(bn) to program the 4th terminal to a parameter. However, the AMS netlister in cadence doesn't allow progn and suggests using inherited connections. I don't want to go through hundreds of schematics and use netSet to set the connection for the 4th connection. Is there any way to map this fourth (invisible) terminal to the property bn?

Title: Re: Verilog AMS netlisting and three terminal devi
Post by Andrew Beckett on Jul 7^th, 2004, 9:37pm

This isn't supported with the "spectre" netlister either - you must be using the obsolete "spectreS" interface?

In theory you could add bn support with a custom AMS netlist procedure (I've done the same for transition of existing spectreS based designs to spectre, with the view that any new schematics should use the inherited connection approach). I've not tried this with AMS though, but it ought to be possible.

However, remember that netSets do not have to be on every instance - if all instances in a block have their bn set to (say) vss!, you can put the netSet on an instance of the block (or even further up the hierarchy) and all child instances will inherit the netSet. In essence a netExpression can be resolved by the first netSet found looking upwards in the hierarchy. Put another way, if every single 3 terminal device is connected to the same net, you could put a single netSet on an instance of the top level block, and that would work.

Of course, if you have individual overrides, you'll need to handle that, but for most cases people use 3 terminal devices where the bulk is connected to a supply or explicit bulk connection into a block; if they want to wire it to a local net, they'd use a 4 terminal device to make it clearer in the schematic (at least, this is good practice - there will always be cases where it doesn't get done like this).

Regards,

Andrew.

Title: Re: Verilog AMS netlisting and three terminal devi
Post by aznaragorn on Jul 14^th, 2004, 8:09am

Unfortunately with the schematics I am working with, the bulk is never really attached to the same thing; our design engineers prefer three terminal devices to save clutter.

However, by changing the parameter bn to type nodeset and editing the spectre stopping view with a netexpression refering to bn, I have got 3 terminal devices to work as they did previously.