Application Notes:
Tester-specific App Notes
Translating WGL/STIL Vector Files to HP83000/93000 Tester Formats
SYNOPSIS
The most common vector formats produced by today’s leading
ATPG tools are WGL and STIL. The WGL format syntax was originally
developed by TSSI and has become somewhat of a defacto industry
standard. Virtually all ATPG tools in use today can generate vectors
in this format (although not all follow the syntax strictly). STIL
(Standard Test Interface Language) is a recently IEEE-adopted standard
format for test vectors that is growing in use. Many ATPG tools
offer the user the option of generating vector files in either of
these two formats. This Application Note focuses on the task of
translating vector files in these formats to test programs for the
HP83000 and 93000 testers (the actual ASCII vector data formats
are the same for both testers).
OVERVIEW
Vtran makes the task of translating WGL and STIL files into HP83000/93000
test programs relatively simple. Canned readers for both of these
formats are included with the vtran product bundle. As long as the
WGL and STIL files follow the syntax of their respective specifications,
the readers can easily handle them. If the WGL file is being generated
from the Synopsys TetraMAX ATPG tool, then it is important to make
sure that the option settings are such that they produce a syntactically
and semantically correct WGL file. A number of the user-controlled
options will result in an invalid WGL file. The option settings
currently recommended for TetraMAX are as follows:
set wgl -bidi_map -x -x
set wgl -bidi_map z- z-
set wgl -bidi_map 0x 0x
set wgl -bidi_map 1x 1x
set wgl -bidi_map xx xx
set wgl -bidi_map z0 z0
set wgl -bidi_map z1 z1
set wgl -bidi_map zx zx
set wgl -bidi_map zz zz
set wgl -chain_list shift
set wgl -group_bidis
set wgl -inversion_reference master
set wgl -last_scan
set wgl -nomacro
set wgl -nopad
set wgl -pre_measured
set wgl -scan_map dash
These settings are applicable to TetraMAX version 2.02 and later. See also the online help notes within the TetraMAX environment.
For STIL vector files, the optional "ScanStructures" block must be present. The information contained in this block is needed by the reader to fully maintain the scan data during translation to the tester formats.
The vector translation process is divided into three separate tasks or blocks, which correspond to the three blocks in the vtran command file — the OVF_BLOCK, the PROC_BLOCK and the TVF_BLOCK. The commands and parameters in these blocks direct the details of the translation. In general, the OVF_BLOCK contains information necessary for vtran to read the input file or "Original Vector File" (i.e. the WGL or STIL file). The PROC_BLOC contains commands that tell vtran what data processing functions you want performed on the simulation data during translation. These typically would be instructions such as how you would like state characters mapped between the input and output formats, or perhaps some desired signal masking. For both of these cycle-based formats, there is not very much processing that needs to be done so the OVF_BLOCK and PROC_BLOCK are typically small. Finally, the TVF_BLOCK contains commands that specify the desired output format — in this case it is the HP format for either the HP83000 or HP93000 testers. There may also be some final processing to be done or some optional user-supplied parameters that appear in the TVF_BLOCK. Now, let’s take a look at some specifics for these translations.
THE OVF_BLOCK
When using the vtran WGL or STIL canned reader, there is actually
very little information (in the way of command instructions) needed
by vtran to read the data and do any necessary mapping of state
characters, in preparation for generating the HP test vector file.
In fact, the only command required in the OVF_BLOCK would be a "TABULAR_FORMAT"
command, which might look like:
OVF_BLOCK
BEGIN
TABULAR_FORMAT wgl —cycle,
-scan;
END
When reading STIL files, simply replace the "wgl" with
"stil". If the name of the cycle-based file is being supplied
from the command line, then this is all that is needed in the OVF_BLOCK.
Otherwise we might add the ORIG_FILE command to this block:
OVF_BLOCK
BEGIN
TABULAR_FORMAT wgl —cycle,
-scan;
ORIG_FILE = "filename";
END
Note the two flags that are being passed to the readers. The first
flag (-cycle) is required and tells the reader to not flatten-out
the timing in the input file. Since the HP test vector files are
cycle-based formats (as are WGL and STIL), this flag instructs the
reader to keep the signal timing information separate from the cycle
vector data. The second flag (-scan) is optional. If there is no
scan data in the input files, then this flag does nothing and could
hence be left out. If the input WGL or STIL vector files do contain
scan data, then this flag instructs the reader to maintain this
scan data as separate data structures, to be passed to the HP-formatted
vectors as scan data. In general, this is a desirable thing to do
since the resulting vector files are usually significantly smaller
using scan syntax than without it. If, however, the user wishes
the scan data contained in the input WGL or STIL files to be expanded
into normal sequential vectors in the HP test vector files, then
this flag can be omitted. It is normally recommended that both of
these flags be used.
THE PROC_BLOCK
The PROC_BLOCK commands required for translating WGL or STIL files
to HP83000/93000 tester files will depend on which input file format
is being read, and on how the state characters have been defined
for the HP testers . If we are mapping WGL state characters to those
needed for HP83000/93000, then a typical mapping might look like:
PROC_BLOCK
BEGIN
STATE_TRANS pure_inputs
‘-‘->’0’, ‘X’->’0’;
STATE_TRANS bidir_inputs
‘-‘->’Z’;
STATE_TRANS outputs ‘0’->’L’,
‘1’->’H’,
‘-‘->’X’, ‘Z’->’M’;
END
These HP83000/93000 state characters are consistent with those commonly
used and match the defaults used by vtran when generating an optional
DVC file (described later). This state mapping is only suggested.
It accomplishes two things — first it maps WGL state characters
to their equivalent default HP characters, and second it maps any
undefined states on input pins to logic 0 (to avoid any floating
inputs). The user may wish to modify these to achieve some other
desired behavior, or if a custom DVC file is being used which defines
other state characters. Mapping the state characters from a STIL
file takes a bit more work:
PROC_BLOCK
BEGIN
STATE_TRANS pure_inputs ‘U’->’1’,
‘D’->’0’, ‘?’->’0’;
STATE_TRANS bidir_inputs ‘U’->’1’,
‘D’->’0’, ‘?’->’Z’;
STATE_TRANS outputs ‘T’->’X’,
‘x’->’X’,‘l’->’L’,
‘h’->’H’,
‘t’->’X’, ‘R’->’L’,
‘G’->’H’,
‘Q’->’X’,
‘?’->’X’;
END
Here we need to be careful about how we map the numerous state characters
in a STIL file to those being used by the HP testers. Again, this
is only a suggested mapping, the user may want to modify this for
different behavior.
THE TVF_BLOCK
There is really only one command required in the TVF_BLOCK of the
vtran command file for the generation of an HP83000/93000 vector
file. This is the TESTER_FORMAT (or SIMULATOR) command, which specifies
the target vector file format. The syntax for this command (and
the optional [ ] parameters) is:
SIMULATOR HP83000 { or HP93000 }
[, -DISABLE_REPEATS]
[, -AUTO_GROUP
]
[, SCANIN_DEFAULT="0"]
[, USE_TIMESET="tset"]
[, MAX_LINE_LENGTH="nn"]
[, REPEAT_THRESHOLD
= "nn"]
[, TIME_STAMPS
= "ON" | "OFF"]
[, AUTO_SCAN_PINS_IN
= "pin"]
[, AUTO_SCAN_PINS_OUT
= "pin"]
[, DVC_FILE="fname"]
[, CONFIG_FILE="fname"]
{ not currently used }
;
While translating WGL or STIL vectors to HP tester formats, vtran
will automatically look for vectors that are repeated in the vector
stream, and optionally use the Repeat function to minimize vector
file size. This activity can be disabled using the —DISABLE_REPEATS
flag. The REPEAT_THRESHOLD parameter can also be used to control
how many successive identical vectors will cause the Repeat function
to be activated — the default is 2. For example, if we set
the REPEAT_THRESHOLD to "10", whenever 10 or more successive
vectors are identical, then the Repeat function would be used to
collapse them. The —AUTO_GROUP flag causes vtran to try and
organize the signals into groups for legibility using a simple algorithm.
When padding unequal length scan chains, the default pad character
is ‘0’, but this can be modified with the SCANIN_DEFAULT
parameter. The USE_TIMESET parameter is used primarily when translating
print-on-change vectors where there is no timing information being
provided in the vector file — it is not normally used when
translating WGL or STIL files where this information is provided.
The MAX_LINE_LENGTH parameter can be used to specify the maximum
number of characters per line in the HP vector file — the default
is 80.
For debugging and analysis, it is often useful to see the timestamps
for each vector in the test program that corresponds to its cycle
time in the WGL or STIL input file. These timestamps are displayed
as comments in the output file, but can be disabled using the TIME_STAMPS
= "OFF" parameter. When translating vectors from a source
which does not explicitly have scan vectors defined but may have
scan activity imbedded in them (this might happen in a VCD input
file), then the AUTO_SCAN_PINS_IN and AUTO_SCAN_PINS_OUT parameters
can be used to tell the HP testers to try using AUTO_SCAN mode to
extract the scan activity. These parameters are not normally used
with WGL or STIL files from an ATPG tool.
The DVC file will only be created if the DVC_FILE parameter is specified
with a file name. The pin timing in this file is expressed in terms
which are relative to the CYCLE time (period) of the vectors. The
interface supports multiple timesets. For scan chains, all chains
are grouped into a single scan_template and are defined with scan
lengths equal to the longest chain. During scan operations, scan
chains which are shorter get padded appropriately.
SOME EXAMPLES
This first example illustrates the translation of a WGL file to
HP83000 vector file. This WGL file happens to contain some scan
vector data. Any input pins that are undefined in the WGL file are
being mapped to a logic ‘0’ in the test program. A timing
file is being generated in "s2.dvc".
ovf_block
begin
orig_file
"s2.wgl";
tabular_format
wgl —cycle, -scan ;
end
proc_block
begin
disable_vector_filter;
STATE_TRANS
pure_inputs ‘-‘->’0’, ‘X’->’0’;
STATE_TRANS
bidir_inputs ‘-‘->’Z’;
STATE_TRANS
outputs ‘0’->’L’, ‘1’->’H’,
‘-‘->’X’, ‘Z’->’M’;
end
tvf_block
begin
tester_format
hp83000 -auto_group,
SCANIN_DEFAULT
= "1",
DVC_FILE="s2.dvc",
REPEAT_THRESHOLD
= "32",
;
target_file
= "s2.83000";
end;
end;
This next example illustrates the translation of a STIL vector file
with scan data, to an HP93000 tester format. As indicated above,
the state translations are a bit more complicated since there are
more potential states in the STIL file. The state translations shown
assume the typical HP93000 state characters are being used. Here
we are also generating a timing file. Each vector line is limited
to 64 characters in length to make the file more easily readable
and printable.
ovf_block
begin
tabular_format stil -cycle
-scan;
orig_file = "s6.stil" ;
end;
proc_block
begin
state_trans pure_inputs 'D'->'0',
'U'->'1', '?'->'0';
state_trans bidir_inputs 'D'->'0',
'U'->'1', '?'->'X';
state_trans outputs 'T'->'X',
'x'->'X',
'l'->'L', 'h'->'H',
't'->'X', 'R'->'L',
'G'->'H', 'Q'->'X',
'?'->'X';
end;
tvf_block
tester_format HP93000
-AUTO_GROUP,
DVC_FILE = "s6.tms",
MAX_LINE_LENGTH
= "64",
TIME_STAMPS = "OFF"
;
target_file = "s6.hp93";
end;
end;
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