GDSII format

 

GDSII format

 

INDEX

 

1. introduction
2. bachus nauer forms
3. GDSII BNF
4. Record header
5. Data types
6. record types overview
7. record types description
8. example file

 

example

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1. text presentation of GDSII file in  KEYformat
2. hex presentation of same file
3. GDSII file

 
 

introduction

GDSII Stream format is the standard file format for transfering/archiving 2D graphical design data. It contains a hiearchy of structures, each structure containing elements (boundary/polygon, path/polyline, text,box, structure references, structure array references). The elements are situated on layers. It is a binary format that is platform independent, because it uses internally defined formats for its data types. While reading GDSII files, the GDSII internal data types (like reals, integers etc.) need to be converted to the platform/CAE package datatypes that are used.The GDSII format is a sequential list of records, each record contains a header to tell what information is in the record.The order of the record needs to be according to the GDSII BNF, because of this strict organization it is relativly easy to parse. The maximum number of vertixes is officially only 200 x,y pairs, but many packages can read up to the absolute maximum of 64k/2=32k, simple because this is the maximum record lenght that can be specified (two bytes).The format is hard to read, since it is binary, for that viewers are available to view (boolean)  the contents as ASCII. Also an ASCII format has been developed (KEY format) which is more than just a text representation. It is possible to convert GDSIIformat  to  KEYformat and back. KEYformat has extended the basic primitives to contain cicrles, arcs, polygons/polylines with arc segments.

Bachus Nauer Forms

The Bachus Nauer Form uses the following symbols:

Symbol Name	Symbol	Meaning
Double Colon	::	"Is composed of."
Square brackets	[ ]	An element which can occor zero or one time.
Braces	{ }	Choose one of the elements within the braces.
Braces with an asteriks	{ }*	The elements within the braces can occur zero or more times.
Braces with a plus	{ }+	The elements within braces must occur one or more times.
Angle brackets	< >	These elements are further defined as a seperate entitie in the syntax list.
Vertical bar	|	Or

 

GDSII BNF

The following is the Bachus Naur Form of the GDSI format, the words in capital are the names of RECORDS

<stream format>	::=	HEADER BGNLIB LIBNAME [REFLIBS] [FONTS]  [ATTRTABLE] [GENERATIONS] [<FormatType>]  UNITS {<structure>}* ENDLIB
<FormatType>	::=	FORMAT | FORMAT {MASK}+ ENDMASKS
<structure>	::=	BGNSTR STRNAME [STRCLASS] {<element>}* ENDSTR
<element>	::=	{<boundary> | <path> | <sref> | <aref> | <text> | <node> | <box>} {<property>}* ENDEL
<boundary>	::=	BOUNDARY [ELFLAGS] [PLEX] LAYER DATATYPE XY
<path>	::=	PATH [ELFLAGS] [PLEX] LAYER DATATYPE [PATHTYPE][WIDTH] XY
<sref>	::=	SREF [ELFLAGS] [PLEX] SNAME [<strans>] XY
<aref>	::=	AREF [ELFLAGS] [PLEX] SNAME [<strans>] COLROW XY
<text>	::=	TEXT [ELFLAGS] [PLEX] LAYER <textbody>
<node>	::=	NODE [ELFLAGS]. [PLEX] LAYER NODETYPE XY
<box>	::=	BOX [ELFLAGS] [PLEX] LAYER BOXTYPE XY
<textbody>	::=	TEXTYPE [PRESENTATION] [PATHTYPE] [WIDTH] [<strans>] XY STRING
<strans>	::=	STRANS [MAG] [ANGLE]
<property>	::=	PROPATTR PROPVALUE

 

Record header

The Stream format output file is composed of variable length records. Record length is measured in bytes. The minimum record length is four bytes. Within the record, two bytes (16 bits) is a word. The 16 bits in a word are numbered 0 to 15, left to right.The first four bytes of a record compose the recordheader. The first two bytes of the recordheader contain a count (in eight-bit bytes) of the total record length, so the maximum length is 65536 (64k). The next record starts immediately after the last byte of the previous record.The third byte of the header is the record type. The fourth byte of the header identifies the type of data contained within the record. The fifth until count bytes of a record contain the data.

Bitnr	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15
Word1	Total Record length in bytes
Word2	Record Type								Data type
Word3	Data until Word n (total record length/2)

 

Data Types

The fourth byte in the record header contains the data type for the rest of the record. The record length is used to find the number of  items of the specified datatype.

Data Type	Value
No Data	0
Bit Array	1
Two Byte Signed Integer	2
Four Byte Signed Integer	3
Four Byte Real	4 (not used)
Eight Byte Real	5
ASCII string	6

 

1. Bit Array:
2. A bit array is a word which uses the value of a particular bit or group of bits to represent data. A bit array allows oneword to represent a number of simple pieces of information.
    
3. Two-Byte Signed Integer:
4. 2-byte integer = 1 word 2s-complement representation. The range of two-byte signed integers is -32,768 to 32,767.

   The following is a representation of a two-byte integer, where S is the sign and M is the magnitude.

   smmmmmmm mmmmmmmm

   The following are examples of two-byte integers:

   00000000 00000001 = 1
   00000000 00000010 = 2
   00000000 10001001 = 137
   11111111 11111111 = -1
   11111111 11111110 = -2
   11111111 01110111 = -137
    

5. Four-Byte Signed Integer:
6. 4-byte integer = 2 word 2s-complement representation

   The range of four-byte signed integers is -2,147,483,648 to 2,147,483,647.

   The following is a representation of a four-byte integer, where S is the sign and M is the magnitude.

   smmmmmmm mmmmmmmm mmmmmmmm mmmmmmmm

   The following are examples of four-byte integers:

   00000000 00000000 00000000 00000001 = 1
   00000000 00000000 00000000 00000010 = 2
   00000000 00000000 00000000 10001001 = 137
   11111111 11111111 11111111 11111111 = -1
   11111111 11111111 11111111 11111110 = -2
   11111111 11111111 11111111 01110111 = -137
    

7. Four-Byte Real
8. 4-byte real = 2-word floating point representation

   (See 5.)
    

9. Eight-Byte Real
10. 8-byte real = 4-word floating point representation

    For all non-zero values:

    1. A floating point number has three parts: the sign, the exponent, and the mantissa.
    2. The value of a floating point number is defined as:
    3. (Mantissa) x (16 raised to the true value of the exponent field).
    4. The exponent field (bits 1-7) is in Excess-64 representation.
    5. The 7-bit field shows a number that is 64 greater than the actual exponent.
    6. The mantissa is always a positive fraction >=1/16 and <1. For a 4-byte real, the mantissa is bits 8-31. For an 8-byte real, the mantissa is bits 8-63.
    7. The binary point is just to the left of bit 8.
    8. Bit 8 represents the value 1/2, bit 9 represents 1/4, etc.
    9. In order to keep the mantissa in the range of 1/16 to 1, the results of floating point arithmetic are normalized. Normalization is a process where by the mantissa is shifted left one hex digit at a time until its left FOUR bits represent a non-zero quantity. For every hex digit shifted, the exponent is decreased by one. Since the mantissa is shifted four bits at a time, it is possible for the left three bits of the normalized mantissa to be zero. A zero value, also called true zero, is represented by a number with all bits zero.
    The following are representations of 4-byte and 8-byte reals, where S is the sign, E is the exponent, and M is the magnitude. Examples of 4-byte reals are included in the following pages, but 4-byte reals are not used currently. The representation of the negative values of real numbers is exactly the same as the positive, except that the highest order bit is 1, not 0. In the eight-byte real representation, the first four bytes are exactly the same as in the four-byte real representation. The last four bytes contain additional binary places for more resolution.

    4-byte real:

    SEEEEEEE MMMMMMMM MMMMMMMM MMMMMMMM

    8-byte real:

    SEEEEEEE MMMMMMMM MMMMMMMM MMMMMMMM MMMMMMMM MMMMMMMM MMMMMMMM

    Examples of 4-byte real:

    Note: In the first six lines of the following example, the 7-bit exponent field = 65. The actual exponent is 65-64=1.

    01000001 00010000 00000000 00000000 = 1
    01000001 00100000 00000000 00000000 = 2
    01000001 00110000 00000000 00000000 = 3
    11000001 00010000 00000000 00000000 = -1
    11000001 00100000 00000000 00000000 = -2
    11000001 00110000 00000000 00000000 = -3
    01000000 10000000 00000000 0000000 = 0 .5
    01000000 10011001 10011001 1001100 = 1 .6
    01000000 10110011 00110011 0011001 = 1 .7
    01000001 00011000 00000000 00000000 = 1.5
    01000001 00011001 10011001 10011001 = 1.6
    01000001 00011011 00110011 00110011 = 1.7
    00000000 00000000 00000000 00000000 = 0
    01000001 00010000 00000000 00000000 = 1
    01000001 10100000 00000000 00000000 = 10
    01000010 01100100 00000000 00000000 = 100
    01000011 00111110 00000001 00000000 = 1000
    01000100 00100111 00010000 00000000 = 10000
    01000101 00011000 01101010 00000000 = 100000
     

11. ASCII String
12. A collection of ASCII characters, where each character is represented by one byte. All odd length strings must be padded with a null character (the number zero), and the byte count for the record containing the ASCII string must include this null character. Stream read-in programs must look for the null character and decrease the length of the string by one if the null character is present.

 

Record Types Overview

The following table gives an overview of all the record that are used within a GDSII file.

Nr.	Code	Mnemonic	Data Type	description
0	0002	HEADER	Two-Byte Signed Integer	version number
1	0102	BGNLIB	Two-Byte Signed Integer	begin of library, last modification date and time
2	0206	LIBNAME	Two-Byte Signed Integer	name of library
3	0305	UNITS	Eight-Byte Real	user and database units
4	0400	ENDLIB	No Data	end of library
5	0502	BGNSTR	Two-Byte Signed Integer	begin of structure + creation and modification time
6	0606	STRNAME	ASCII string	name of structure
7	0700	ENDSTR	No Data	end of structure
8	0800	BOUNDARY	No Data	begin of boundary element
9	0900	PATH	No Data	begin of path element
10	0A00	SREF	No Data	begin of structure reference element
11	0B00	AREF	No Data	begin of array reference element
12	0C00	TEXT	No Data	begin of text element
13	0D02	LAYER	Two-Byte Signed Integer	layer number of element
14	0E02	DATATYPE	Two-Byte Signed Integer	Datatype number of element
15	0F03	WIDTH	Four-Byte Signed Integer	width of element in db units
16	1003	XY	Four-Byte Signed Integer	list of xy coordinates in db units
17	1100	ENDEL	No Data	end of element
18	1206	SNAME	ASCII string	name of structure reference
19	1302	COLROW	Two-Byte Signed Integer	number of colomns and rows in array reference
21	1500	NODE	No Data	begin of node element
22	1602	TEXTTYPE	Two-Byte Signed Integer	texttype number
23	1701	PRESENTATION	Bit Array	text presentation, font
25	1906	STRING	ASCII string	character string for text element
26	1A01	STRANS	Bit Array	array reference, structure reference and text transform flags
27	1B05	MAG	Eight Byte Real	magnification factor for text and references
28	1C05	ANGLE	Eight Byte Real	rotation angle for text and references
31	1F06	REFLIBS	ASCII string	name of referenced libraries
32	2006	FONTS	ASCII string	name of text fonts definition files
33	2102	PATHTYPE	Two-Byte Signed Integer	type of PATH element end ( rounded, square)
34	2202	GENERATIONS	Two-Byte Signed Integer	number of deleted structure ?????
35	2306	ATTRTABLE	ASCII string	attribute table, used in combination with element properties
38	2601	ELFLAGS	Two-Byte Signed Integer	template data
42	2A02	NODETYPE	Two-Byte Signed Integer	node type number for NODE element
43	2B02	PROPATTR	Two-Byte Signed Integer	attribute number
44	2C06	PROPVALUE	ASCII string	attribute name
45	2D00	BOX	No Data	begin of box element
46	2E02	BOXTYPE	Two-Byte Signed Integer	boxtype for box element
47	2F03	PLEX	Four-Byte Signed Integer	plex number
50	3202	TAPENUM	Two-Byte Signed Integer	Tape Number
51	3302	TAPECODE	Two-Byte Signed Integer	Tape code
54	3602	FORMAT	Two-Byte Signed Integer	format type
55	3706	MASK	ASCII string	list of layers
56	3800	ENDMASKS	No Data	end of MASK

 

Record types description

Records are always an even number of bytes long. The first four bytes of a record are the  record header. If a record contains ASCII string data and the ASCII string is an odd number of bytes long, the data is padded with a null character. This paragraph lists the record types with a brief description of each. The descriptions include the record name and a four-digit number in brackets. The first two numbers within the brackets are the record type, and the last two numbers in brackets are the data type. All record numbers are expressed in hexadecimal.
 

0

HEADER

0002

Two-Byte Signed Integer

Contains two bytes of data representing the Stream version number.
 

1

BGNLIB

0102

Two-Byte Signed Integer

Contains the last modification time of a library (two bytes each for year, month, day, hour, minute, and second), the time of last access (same format), and marks the beginning of a library.

Bit

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

word1

l C (hex) # of bytes in record

word2

01 (hex) 02 (hex)

word3

year (lastmodification time)

word4

month

word5

day

word6

hour

word7

minute

word8

second

word9

year (last access time)

word10

month

word11

day

word12

hour

word13

minute

word14

second

 

2

LIBNAME

0206

ASCII String

Contains a string which is the library name. The library name must follow UNIX filename conventions for length and valid characters. The library name may include the file extension (.sf or db in most cases).
 

3

UNITS

0305

Eight-Byte Real

Contains two eight-byte real numbers. The first number is the size of a database unit in user units. The second number is the size of a database unit in meters. For example, if you create a library with the default units (user unit = 1 micron and 1000 database units per user unit), the first number is .001, and the second number is 1E-9. Typically, the first number is less than 1, since you use more than 1 database unit per user unit. To calculate the size of a user unit in meters, divide the second number by the first.
 

4

ENDLIB

0400

No Data

Marks the end of a library.
 

5

BGNSTR

0502

Two-Byte Signed Integer

Contains the creation time and last modification time of a structure (in the same format as the BGNLIB record), and marks the beginning of a structure.
 

6

STRNAME

0606

ASCII String

Contains a string which is the structure name. A structurename may be up to 32 characters long. Legal structurename characters are:

• A through Z
• a through z
• 0 through 9
• Underscore (_)
• Question mark (?)
• Dollar sign ($)

 

7

ENDSTR

0700

No Data

Marks the end of a structure.
 

8

BOUNDARY

0800

No Data

Marks the beginning of a boundary element.
 

9

PATH

0900

No Data

Marks the beginning of a path element.
 

10

SREF

0A00

No Data

Marks the beginning of an Sref (structure reference) element.
 

11

AREF

0B00

No Data

Marks the beginning of an Aref (array reference) element.
 

12

TEXT

0C00

No Data

Marks the beginning of a text element.
 

13

LAYER

0D02

Two-Byte Signed Integer

Contains two bytes which specify the layer. The value of the layer must be in the range of 0 to 255.
 

14

DATATYPE

OEO2

Two-Byte Signed Integer

Contains two bytes which specify the datatype. The value of the datatype must be in the range of 0 to 255.
 

15

WIDTH

0F03

Two-Byte Signed Integer

Contains four bytes which specify the width of a path or text lines in database units. A negative value for width means that the width is absolute, that is, the width is not affected by the magnification factor of any parent reference. If omitted, zero is assumed.
 

16

XY

1003

Two-Byte Signed Integer

 
轉存失敗重新上傳取消

• Contains an array of XY coordinates in database units. Each X or Y coordinate is four bytes long. Path elements may have a minimum of 2 and a maximum of 200 coordinates. Boundary and border elements may have a minimum of 4 and a maximum of 200 coordinates. The first and last coordinates of a boundary or border must coincide.
• A text, or Sref element may have only one coordinate.
• An Aref has exactly three coordinates. In an Aref, the first coordinate is the array reference point (origin point). The other two coordinates are already rotated, reflected as specified in the STRANS record (if specified). So in order to calculate the intercolomn and interrow spacing, the coordinates must be mapped back to their original position, or the vector lenght (x1,y1-> x3,y3) must be divided by the number of row etc. . The second coordinate locates a position which is displaced from the reference point by the inter-column spacing times the number of columns. The third coordinate locates a position which is displaced from the reference point by the inter-row spacing times the number of rows. For an example of an array lattice see the next picture.
• Aref rotated -30 degrees.
• A node may have from one to 50 coordinates.
• A box must have five coordinates, with the first and last coordinates being the same.

 

17

ENDEL

1100

No Data

Marks the end of an element.

18

SNAME

1206

ASCII string

Contains the name of a referenced structure.See also STRNAME.

19

COLROW

1302

Two-Byte Signed Integer

Contains four bytes. The first two bytes contain the number of columns in the array. The third and fourth bytes contain the number of rows. Neither the number of columns nor the number of rows may exceed 32,767 (decimal), and both are positive. See also AREF.
 

21

NODE

1500

No Data

Present Marks the beginning of a node
 

22

TEXTTYPE

1602

Two-Byte Signed Integer

Contains two bytes representing texttype. The value of the texttype must be in the range 0 to 255.
 

23

PRESENTATION

1701

Bit Array

Contains one word (two bytes) of bit flags for text presentation. Bits 10 and 11, taken together as a binary number, specify the font (00 means font 0, 01 rneans font 1, 10 means font 2, and 11 means font 3). Bits 12 and 13 specify the vertical justification (00 means top, 01 means middle, and 10 means bottom). Bits 14 and 15 specify the horizontal justification (00 means left, 01 means center, and 10 means right). Bits 0 through 9 are reserved for future use and must be cleared. If this record is omitted, then top-left justification and font 0 are assumed. The following shows a PRESENTATION record.
 

Bit	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15
word1	6 (hex) # of bytes in record
word2	17 (hex)								01 (hex)
word3	unused										font number		vertical  presentaion		horizontal presentation

 

25

STRING

1906

ASCII String

Contains a character string, up to 512 characters long, for text presentation.
 

26

STRANS

1A01

Bit Array

Contains two bytes of bit flags for Sref, Aref, and text transforrnation. Bit 0 (the leftmost bit) specifies reflection. If bit 0 is set, the element is reflected about the X-axis before angular rotation. For an Aref, the entire array is reflected, with the individual array members rigidly attached. Bit 13 flags absolute magnification. Bit 14 flags absolute angle. Bit 15 (the rightmost bit) and all remaining bits are reserved for future use and must be cleared. If this record is omitted, the element is assumed to have no reflection, non-absolute magnification, and non- absolute angle.
The following shows a STRANS record.
 

Bit	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15
word1	6 (hex) # of bytes in record
word2	1A (hex)								01 (hex)
word3	reflection	unused												absolute  magnification	absolute angle	unused

 

27

MAG

1B05

Eight Byte Real

Eight-Byte Real Contains a double-precision real number (8 bytes), which is the magnification factor. If this record is omitted, a magnification factor of one is assumed.
 

28

ANGLE

1C05

Eight Byte Real

Eight-Byte Real Contains a double-precision real number (8 bytes), which is the angular rotation factor. The angle of rotation is measured in degrees and in the counterclockwise direction. For an Aref, the ANGLE rotates the entire array (with the individual array members rigidly attached) about the array reference point. For COLROW record information, the angle of rotation is already inlcuded in the coordinates. If this record is omitted, an angle of zero degrees is assumed.
 

31

REFLIBS

1F06

ASCII String

Contains the names of the reference libraries. This record must be present if any reference libraries are bound to the working library. The name of the first reference library starts at byte 5 (immediately following the record header) and continues for 44 bytes. The next 44 bytes contain the name of the second library. The record is extended by 44 bytes for each additional library (up to 15) which is bound for reference. The reference library names may include directory specifiers (separated with "/") and an extension (separated with "."). If either the first or second library is not named, its place is filled with nulls.
 

32

FONTS

2006

ASCII String

Contains the names of the textfont definition files. This record must be present if any of the four fonts have acorresponding textfont definition file. This record must not be present if none of the fonts have a textfont definition file. The textfont filename of font 0 starts the record, followed by the textfont files of the remaining three fonts.Each filename is 44 bytes long. The filename is padded withnulls if the name is shorter than 44 bytes. The filename is null if no textfont definition corresponds to the font. The textfont filenames may include directory specifiers (separated with "/" and an extension (separated with ".").
 

33

PATHTYPE

2102

Two-Byte Signed Integer

This record contains a value that describes the type of path endpoints. The value is

• 0 for square-ended paths that endflush with their endpoints
• 1 for round-ended paths
• 2 for square-ended paths that extend a half-width beyond their endpoints

If not specified, a Path-type of 0 is assumed.

The following picture shows the pathtypes
 

轉存失敗重新上傳取消	Pathtype 0 produces a square-ended path, ending flush with thedigitized endpoints. This is the de-fault pathtype if none is specified
	Pathtype 1 produces a round-ended path. The two ends aresemicircular with center at thedigitized endpoints.
	Pathtype 2 produces a square-ended path. The ends of the pathextend beyond the digitized end-points by one-half the path width.

 

34

GENERATIONS

2202

Two-Byte Signed Integer

This record contains a value to indicate the number of copies of deleted or back-up structures to retain. This numbermust be at least 2 and not more than 99. If the GENERATION record is omitted, a value of 3 is assumed.
 

35

ATTRTABLE

2306

Two-Byte Signed Integer

Contains the name of the attribute definition file. This record is present only if an attribute definition file is bound to the library. The attribute defenition filename may include directory specifiers (separated with "/") and an extension (separated with "."). Maximum record size is 44 bytes.
 

36

STYPTABLE

2502

Two-Byte Signed Integer

Unrelesed Feature
 

37

STRTYPE

2502

Two-Byte Signed Integer

Unrelesed Feature
 

38

ELFLAGS

2601

Bit Array

Contains two bytes of bit flags. Bit 15 (the rightmost bit)specifies Template data. Bit 14 specifies External data(also referred to as Exterior data). All other bits are currently unused and must be cleared to 0. If this record isomitted, all bits are assumed to be 0. The following shows an ELFLAGS record.

For additional information on Template data, consult the GDSII Reference Manual. For additional information on External data, consult the CustomPlus User's Manual.
 

Bit	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15
word1	6 (hex) # of bytes in record
word2	26 (hex)								01 (hex)
word3	unused														external data	template  data

 

39

ELKEY

2703

Two-Byte Signed Integer

(Unreleased feature)
 

40

LINKTYPE

28

Two-Byte Signed Integer

(Unreleased feature)
 

41

LINKKEYS

29

Two-Byte Signed Integer

(Unreleased feature)
 

42

NODETYPE

2A02

Two-Byte Signed Integer

Contains two bytes which specify nodetype. The value ofthe nodetype must be in the range of 0 to 255.
 

43

PROPATTR

2B02

Two-Byte Signed Integer

Contains two bytes which specify the attribute number. The attribute number is an integer from 1 to 127. Attribute numbers 126 and 127 are reserved for the user integer and userstring (CSD) properties which existed prior to Release 3.0.
 

44

PROPVALUE

2C06

ASCII string

Contains the string value associated with the attribute named in the preceding PROPATTR record. Maximumlength is 126 characters. The attribute-value pairs associated with any one element must all have distinct attribute numbers. Also, the total amount of property data that may be associated with any one element is limited: thetotal length of all the strings, plus twice the number of attribute-value pairs, must not exceed 128 (or 512 if the element is an Sref, Aref, contact, nodeport, or node).

For example, if a boundary element uses property attribute2 with property value "metal," and property attribute 10 with property value "property," the total amount of property data is 18 bytes. This is 6 bytes for "metal" (odd-length strings must be padded with a null) + 8 for "property" + 2 times the 2 attributes (4) = 18.
 

45

BOX

2D00

No Data

Marks the beginning of a box element.
 

46

BOXTYPE

2E02

Two-Byte Signed Integer

Contains two bytes which specify boxtype. The value of the boxtype must be in the range of 0 to 255.
 

47

PLEX

2F03

Two-Byte Signed Integer

A unique positive number which is common to all elementsof the plex to which this element belongs. The head of the plex is flagged by setting the seventh bit; therefore, plexnumbers should be small enough to occupy only the right-most 24 bits. If this record is not present, the element is not a plex member Applies to Pathtype 4.Contains four bytes which specify indatabase units the distance a path outline begins before orafter the last point of the path. Value can be negative.
 

50

TAPENUM

3202

Two-Byte Signed Integer

Contains two bytes which specify the number of the current reel of tape for a multi-reel Stream file. For the first tape, the TAPENUM is 1: for the second tape, the TAPENUM is 2. For each additional tape, increment the TAPENum by one.
 

51

TAPECODE

3302

Two-Byte Signed Integer

Contains 12 bytes. This is a unique 6-integer code which iscommon to all the reels of multi-reel Stream file. It verifies that the correct reels are being read.
 

52

STRCLASS

3401

Two-Byte Signed Integer

Not used
 

53

RESERVED

3503

Two-Byte Signed Integer

This record type was used for NUMTYPES but was not required.

54

FORMAT

3602

Two-Byte Signed Integer

Defines the format of a Stream tape in two bytes. The possible values are:

1. for GDSII Archive format
2. for GDSII Filtered format
3. for EDSM Archive format
4. for EDSHI Filtered forrnat

An Archive Stream file contains elements for all the layers and data types. In an Archive Stream file, the FORMAT record is followed immediately by the UNITS record. A file which does not have the FORMAT record is assumed to be an Archive file.

A Filtered Stream file contains only the elements on the layers and with the datatypes you specify during creation ofthe Stream file. The list of layers and datatypes specified appear in MASK records. At least one MASK record must immediately follow the FORMAT record. The MASK records are terminated with the ENDMASKS record.
 

55

MASK

3706

ASCII string

(Required for and present only in FilteredStream file. )
Contains the list of layers and datatypes specified by the user when creating the file. At least one MASK record must immediately follow the FORMAT record. More than one MASK record may occur. The last MASK record is followed by the ENDMASK record.
In the MASK list, datatypes are separated from the layers with a semicolon. Individual layers or datatypes are sepa-rated with a space. A range of layers or datatypes is specified with a dash.

An example MASK list looks like this: 1 5 -7 10 ; 0- 255

56

ENDMASKS

3800

NoData

(Required for and present only in FilteredStream file.)
Marks the end of the MASK records. The ENDMASKS record must follow the last MASK record. ENDMASKS is immediately followed by the UNITS record.

 

http://boolean.klaasholwerda.nl/interface/bnf/gdsformat.html