What is a layer map file and when do we need it?

hi there,
what is layer map file and when do we need it? is there any links or documents available? I am really confused about the map file, sometimes you need it to do GDS in/out, sometimes you need not use it to do GDS in/out ? Could someone here give some expert explanation about it ? thanks in advance!

map file for google layer

it should come with your pdk. i dont think theres a standard file extension, i've seen it with .lmt, .map, .strmMapTable... but it is always written in the same format, the column headers are

#cadence name | layer purpose | gds number | data type

for example

poly drawing 1 0
m1 drawing 2 0
etc...

layer map

thanks for your kind reply , but when do we need to use the map file. If we do stream in/out under the same technology, do we need it ? I am looking forward for your further reply, and by the way, what does 'data type' mean in the line: '#cadence name | layer purpose | gds number | data type' ?
regards,
henry

gds layer map file format for cadence virtuoso

1. stream in and stream out from/to gdsii format

2. virtuoso passive component designer emss needs stream table for em simulation (don't have much experience with this tool).

i dont know what 'data type' refers to, I just saw it in the header of all my layer map tables. i'm sure its mentioned in one of the virtuoso layout help files. check this post

stream out + layer map table

hi oermens,
I have cheched the link you post , but there is little information about layer map file. thank you for your reply. can someone here post some other linkds or documents on layer map file or GDSII format, thanks in advance!

map file layer data

henrywent said:

... but there is little information about layer map file ... can someone here post some other linkds or documents on layer map file or GDSII format, thanks in advance!

Click to expand...

There isn't any more in the layer map file than what oermens showed above. Physical layers have layer-type-num=0 , those with layer-type-num>0 are non-physical auxiliary support layers with purposes as, e.g., "pin", "net" (for LVS), "instance", "label", or marking layers for special areas, which require specialized rules for DRC and/or LVS, like "HV", "pad" or "ESD" regions. The related numbers are not fix for a special purpose, hence may be assigned arbitrarily, usually fab-specific.

About GDSII you can find out in WIKI: https://en.wikipedia.org/wiki/GDSII#References
... including references to its format description - if you really want that ;-)
Cheers, erikl

gds2 stream layer numbers

A layer map file maps the GDS2 stream layer numbers and datatypes
to dfII layer names and purpose pairs.

GDS2 has always used Datatype to extend the 63 layer limit which was in place
for many years. There was a Layer Number limit of 63 and each layer number
could have 63 datatypes.

As was already mentioned, the Datatypes used for DFII designs is usually mapping
a layer name and it's layer purpose.

ie.
metal1 drawing 31 0
metal1 pin 31 1

will stream in/out metal1 to layer 31 to two different datatypes (0,1)

When do you need a layer map file?

1) If your DFII techfile does not contain streamLayers in your layerRules section.
If you define streamLayers inside the techfile, these layers will be mapped
automatically to those specified in that section.

2) If you are streaming in IP to a library with different mapping, ie the IP GDS does
not have the same mapping as your streamLayers section, a layer.map file can be used to override or remap the stream layers.

Multiple library vendors may not use the same layer maps for the same foundry
process although they should. This is not always the case.

layer map gds

when ur stream in /out the lmp is must to conver becaus ethe the tool will undersatnd by this file only. when ur mapping from technology to technology u have to feed both the lmp file.

there is another link on this layer map issue.

How to write an output-map file | Circuit Design World