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StefanSchippers / xschem

A schematic editor for VLSI/Asic/Analog custom designs, netlist backends for VHDL, Spice and Verilog. The tool is focused on hierarchy and parametric designs, to maximize circuit reuse.
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Meaning of "+" and "|" in .sch files #186

Closed urish closed 3 months ago

urish commented 3 months ago

Sometimes, there are + or | symbols in the middle of the attr list, e.g.:

https://github.com/StefanSchippers/xschem/blob/aa6182c65f1b0379e13f7180f67e9f7e2dceb9f9/xschem_library/rom8k/rom2_predec3.sch#L128-L130

or

https://github.com/vincentfusco/tt06_555/blob/d58ca5dc6e58d8d6e327737296cf200e120c4b07/xsch/ip/timers/timer_core.sch#L188-L189

What is the meaning of those symbols?

StefanSchippers commented 3 months ago

Hi, I think the | in the second case is a typo. The + in the lvnot.sym is a "spice netlist cognitive bias" + is the character to use when you break a long line in a spice netlist. In this context it is just useless, I think I will remove it in the example circuits. An attribute list is just a string with key=value assignments. Anything else is allowed, if it has not the form key=value it is ignored.

urish commented 3 months ago

An attribute list is just a string with key=value assignments. Anything else is allowed, if it has not the form key=value it is ignored

Thanks! And can the keys have any characters other than } and whitespace? or is there a limited set of characters valid for a key?

StefanSchippers commented 3 months ago

keys can have any characters except newline, backslash, double quote (") , space, tab and ; the { character is allowed (hopefully no one will use it) xschem will escape it when putting the attribute list inside {...}

urish commented 3 months ago

Thanks! The xschem-viewer will now happily accept those files :)

StefanSchippers commented 3 months ago

You are welcome. If you find other unclear things just ask!