tristate or mux2_1 VHDL

[voho]

vhdl de 4 mux2_1

Hi all

Io is clk at 200Mhz ; I1 is clk at 100Mhz i must do use mux2_1 or tristate ?

First vhdl:
output<= I1 when select ='1' else I0;

Second vhdl:
output<= I1 when select ='1' else 'Z';
output<= I0 when select ='0' else 'Z';


Regards

 

[semiconductorman]

mux2_1

Neither ... see u want to make an assignment such that output should be l0 when select = 0 and l1 when select = 0
so
output <= l0 when select = '0' else l1 ;
this should do ... if I have not understood ur problem properly write back pls

 

[voho]

Hi semiconductorman,


output <= l0 when select = '0' else l1 ;
i think it's same:
output <= l1 when select = '0' else l0 ;

Thank's regards

 

[adap]

I think that the first VHDL will do
output<= I1 when select ='1' else I0;

 

[tut]

Hi there,
if u are just trying to simulate, then u can use this simple multiplexor
as is suggested by others..

But if you are targetting it into a FPGA, such asynchronous switching
of clocks can cause glitches

To avoid that use the circuit shown @ **broken link removed**

u can also use BUFGMUX, if the concerned two clocks are external and
you are using Virtex 2 Family..

 

[voho]

hi all,

Thank you very much i used BUFGMUX it's work perfectlly in virtex II

regards

 

[wolfzou]

hi there:
using BUFGMUX is a perfect methord.it can change
oen clock betwent other clock with no screw