Question about r and f for cell delay in PT report

[energeticdin]

Hi
I find that in PT report,
in Data arrival time section
u__RTL_top/../CLK (ARM922T)
2.39 0.00 5.93 f

I find f as there, it mention that f means Cell delay when output pin transition from 1 -> 0

In required section, I find
u__RTL_top/../..DAA_rg_3_/CK RHQX1)
9.08 r
r it mention that r means cell delay when output pin transition from 0 -> 1

why it is coming there?
what exactly means? I am little bit confused here


Thanks
DIN

 

[ac123]

Re: Reg: PT

hi,

I am also new to PT. But let me share what I think about your questions

r means the transition from 0->1 and f means 1->0. Depending on the nature of the pin it can be either input or output transition. For a clock pin it will be the input transition and for a Q pin it is the output transition. Every pin will have rise time and fall time calculated from the .lib and the input slew and output load of the pin which is taken from the current design.

The tool may take the worst case transition time when it does the setup and hold analysis.

I am looking forward to experienced guys' views on this.

 

[lakshman.ar]

Reg: PT

for
1) setup analysis the tool takes the "worst case" values frm the .lib

2) hold analysis the tool takes the "best case" values frm the .lib

means to say tht for setup analysis .. , "r" or "f" which ever value is max, will be take for the DATA PATH & min values will be taken for the CLK PATH ....

setup : datapath ( ARRIVAL TIME) -> MAX values
clockpath ( REQUIRED TIME) -> MIN values

FOR SETUP ANAYSIS, this is the reason, tht u find "arrival section" the tool always takes the WC values and for the " required section" takes the BC values !!!

PS:
IN PT, BY DEFAULT IF UR GIVE THE COMMAND "REPORT TIMNG", THE TOOL ALWAYS GIVES THE REPORT FOR THE SETUP ANALYSIS !!!

WBR,
Lakshman