( ESNUG 388 Item 7 ) --------------------------------------------- [02/27/02]
Subject: ( ESNUG 386 #16 ) BSD Compiler With Core Logic, HIGHZ, & Pull-Ups
> I wouldn't call it perfect as of yet, but BSD Compiler works and it is now
> automated enough that a even co-op student can use it in our design flow.
>
> - Shin Wu, ASIC Division
> Atmel Corporation Columbia, MD
From: Francisco Russi <russi@synopsys.com>
Hi John,
I'd like to address some of the issues Shin Wu from Atmel brought up in
ESNUG 386 #16 reguarding BSD Compiler.
> 1.) BSD Compiler was not able to insert Boundary Scan with the design core
> in the netlist, contrary to BSD Compiler User Guide's claims. We
> overcome this by removing the core before inserting Boundary Scan.
BSD Compiler supports boundary scan logic insertion with or without the
core logic. However, we recommend (but not necessary) our customers to
run the tool without the core logic to avoid any potential run time
performance issue during compliance checking. Running the tool with the
core logic, will impact run times during 1149.1 compliance check, which
uses simulation technique and simulation can create activity within core
logic that is not relevant to compliance checking. This is avoided if
design is used without core logic
> 3.) BSD Compiler had problems with our Synopsys Atmel libraries as well.
> It could not synthesize functional 1149.1 components when input
> buffers supported both true and complementary outputs going into the
> array. It couldn't implement the HIGHZ instruction with bidi buffers.
There were some limitations in implementing the HIGHZ instructions for
complementary ports, which lacked certain special attributes in the library
cell, and could not characterize "bidi buffers formed by combining separate
input and output IO buffer pieces". Although "insert_bsd" was able to
insert the BSR's correctly, the compliance check required a second vector
to properly characterize these pads. We fixed this issue in the 2001.08
release, and a special feature was added to validate pads up front in the
design cycle during "preview_bsd" to let customers know of any pad related
problems early in the design cycle.
> 4.) We still have an outstanding issue with our pullup/pulldown terminators
> which we are trying to get resolved soon. (A workaround for this
> problem is in place until we get a permanent solution from Synopsys.)
BSD Compiler supports library cell pads with internal pull-up and pull-down
resistors. However, pad cells with an external pull-up resistor without a
compliance enable logic to switch off the pull-up for compliance check or
Iddq testing will cause a violation of the 1149.1 standard. The 1149.1
compliance check in BSD Compiler will flag this as a violation to the
Standard since no logic can exist between the pad and the BSR. The
workaround to this issue is to design the pad cell with an internal pull-up,
and use the tool capability to change link libraries for verification.
Once again, I very much appreciate Shin Wu's feedback here on ESNUG.
- Francisco Russi
Synopsys, Inc. Austin, TX
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