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How can I set bus's direction in spicein?

gaojun

Hi,

I'm using spicein to import cdl netlist in virtuoso 6.1.6. It work well for non bus type IO. But if the IO pin in subckt definitation is bus type, for example input<2:0>, and whether I use *.pininfo input:i or *.pininfo input<2:0>:i or *.pininfo input<2>:i input<1>:i input<0>:i, the schematic could not give this pin the correct direction. How can I fix it?

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  • Andrew Beckett

    Yes, but you're relying on a side-effect. It's not legal CDL - all that's happening is that SPICE IN is just taking the pin-name as is, and because it's a bus, it then happens to work. I suspect that the *.PININFO doesn't work because this is unexpected syntax and the colon in the middle of the pin name is confusing it (you have a colon in the name, and as the separator for the pin direction).

    The alternative would be to use this CDL syntax:

    .SUBCKT myblock a b c b1<2:0> / d e f1<3:0>

    Everything before the "/" is an output pin; everything after is an input pin. This works - I tested it. You're still relying on a side-effect of incorrect CDL syntax, but it does happen to work. The "/" is part of the CDL definition to separate outputs from inputs, and if my memory is correct, predates the introduction of *.PININFO which came at a later date (although that's been there for more than 20 years, I'm sure).

    Regards,

    Andrew

Reply
  • Andrew Beckett

    Yes, but you're relying on a side-effect. It's not legal CDL - all that's happening is that SPICE IN is just taking the pin-name as is, and because it's a bus, it then happens to work. I suspect that the *.PININFO doesn't work because this is unexpected syntax and the colon in the middle of the pin name is confusing it (you have a colon in the name, and as the separator for the pin direction).

    The alternative would be to use this CDL syntax:

    .SUBCKT myblock a b c b1<2:0> / d e f1<3:0>

    Everything before the "/" is an output pin; everything after is an input pin. This works - I tested it. You're still relying on a side-effect of incorrect CDL syntax, but it does happen to work. The "/" is part of the CDL definition to separate outputs from inputs, and if my memory is correct, predates the introduction of *.PININFO which came at a later date (although that's been there for more than 20 years, I'm sure).

    Regards,

    Andrew

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