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Altera_Forum
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17 years ago

How does Quartus handle flip flop with both async reset and set

I have come to know that Stratix iii and Iv do not support async set ,so how in Quartus handles simulatanoous reset and set (async) ,I have heard that it uses latch but don't know exactly,Plz do clar...
Altera_Forum's avatar
Altera_Forum
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17 years ago

You could use 2 FF's to screen instead of the latch (for a total of 3) -

always @(posedge clk or posedge aclr) if (aclr) aclr_ff <= 1'b0; else aclr_ff <= 1'b1;

always @(posedge clk or posedge apre) if (apre) apre_ff <= 1'b0; else apre_ff <= 1'b1;

always @(posedge clk) d_ff <= din;

assign q = aclr_ff & (!apre_ff | d_ff);

This isn't exactly equivalent if you clear, then preset before the next clock tick. It also has more timing critical signals to route than the latch version.