Retaining not used nodes

[ALuPin]

Hi,

I have several nodes in my design (registered nodes) which do not have
a "driving" purpose. But for later use of SignalTap (Altera tool to
make internal FPGA nodes visible) I do want the synthesizer
not to optimize these nodes away. On the other hand I do not want
to route these nodes to output pins because of a limited amount of
available pins.

Is there some possibility to avoid that these registerd not used nodes
are optimized away ?

Thank you for your suggestion.

Rgds
André

 

[m]

On 8 Feb 2005 02:43:57 -0800, ALuPin@web.de (ALuPin) wrote:

Hi,

I have several nodes in my design (registered nodes) which do not have
a "driving" purpose. But for later use of SignalTap (Altera tool to
make internal FPGA nodes visible) I do want the synthesizer
not to optimize these nodes away. On the other hand I do not want
to route these nodes to output pins because of a limited amount of
available pins.

Is there some possibility to avoid that these registerd not used nodes
are optimized away ?

Thank you for your suggestion.

Rgds
André

There are synthesis pragmas which you can use to keep these registers
(syn_keep for synplicity etc.). If you have too much difficulty
convincing either the synthesizer or the mapper to keep these unused
registers, you can "or" the outputs of multiple registers and route it
to a single output pin which should vastly reduce your pin
availability concerns.

 

[Christos]

Hi,

One thing that might work is to drive them to outputs and then define those
outputs as virtual pins with the assignment editor.
They will not be synthesised away.

hope this helps.

Christos Zamantzas

"mk" <kal*@dspia.*comdelete> wrote in message
news:ro7h01dckpv186f6el2cn8vjus11s1vvbb@4ax.com...

On 8 Feb 2005 02:43:57 -0800, ALuPin@web.de (ALuPin) wrote:

Hi,

I have several nodes in my design (registered nodes) which do not have
a "driving" purpose. But for later use of SignalTap (Altera tool to
make internal FPGA nodes visible) I do want the synthesizer
not to optimize these nodes away. On the other hand I do not want
to route these nodes to output pins because of a limited amount of
available pins.

Is there some possibility to avoid that these registerd not used nodes
are optimized away ?

Thank you for your suggestion.

Rgds
André

There are synthesis pragmas which you can use to keep these registers
(syn_keep for synplicity etc.). If you have too much difficulty
convincing either the synthesizer or the mapper to keep these unused
registers, you can "or" the outputs of multiple registers and route it
to a single output pin which should vastly reduce your pin
availability concerns.