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tifmdgo01
Observer
Observer
818 Views
Registered: ‎05-23-2017

Whats difference between OBUFDS and user design(invert gate)?

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Hi.

 

Why is the use of OBUFDS recommended?

 

For example....

(1) use invert gate

assign A = OUTPUT

assign a = ~OUTPUT

 

(2) use OBUFDS

OBUFDS #(
   .IOSTANDARD("DEFAULT"), 
   .SLEW("SLOW")
) OBUFDS_inst (
   .O(A),
   .OB(a),
   .I(OUTPUT)
);

 

What is the difference between (1) and (2)?

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lowearthorbit
Scholar
Scholar
807 Views
Registered: ‎09-17-2018

1 is internal to the device,

2 is a differential output buffer driving the external pins of the device.

There are no differential signals internal to the device.

l.e.o

 

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3 Replies
lowearthorbit
Scholar
Scholar
808 Views
Registered: ‎09-17-2018

1 is internal to the device,

2 is a differential output buffer driving the external pins of the device.

There are no differential signals internal to the device.

l.e.o

 

View solution in original post

dpaul24
Scholar
Scholar
803 Views
Registered: ‎08-07-2014

@tifmdgo01,

From the usage perspective, if the RTL is used only for target Xilinx FPGA implementation then use <2>, but for RTL portability maintenence (use in other FPGAs) use <1>.

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tifmdgo01
Observer
Observer
768 Views
Registered: ‎05-23-2017

Thank you 'dpaul24' !

Good Tip!

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