HSPICE node naming convention

spice

I ran a parameter extraction program and its output is expected to be run under HSPICE. It looks similar to this:

.SUBCKT DAC BIT0 BIT1 BIT2 BIT3 BIT4 BIT5 BIT6 BIT7

C1234 BIT0:5 0 1e-12
C4321 BIT0:6 0 5e-12

.ENDS

Why is there a : in the node names as in BIT0:5 and BIT0:6. What are they used for? Do they refer to the same node?

Best Answer

From the hspice perspective and how it simulate circuit BIT0:5 and BIT0:6 are separate nodes.

Regarding the naming convention extraction program try to keep the name of the nodes the same as in schematic(for circuit designer convenience). However sometimes it is not possible -> for example if using RC extraction one metal path will be represented by several cascaded circuits like so:

BIT0       BIT0:1        BIT0:2         BIT0:3
    R1             R2             R3
---/\/\/\----|----/\/\/\----|----/\/\/\---
            ---            ---
       C1   ---         C2 ---
             |              |
            ___            ___

So this naming convention is just a mark that those nets correspond somewhat to schematic net.

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