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Altera_Forum
Honored Contributor
Honored ContributorCounter and time delay
Hi,
I'm very new in Quartus, I just started a couple of days ago. The situation is that I've 4 inputs (only one of these can be active at time) and every time input changes to another, I need to increase the same counter. I've tried to do this with block diagram (I don't know anything about v-files) but I haven't found any counter block. So how I solve this very simple problem? Second, when the input goes high, I need to keep it high only, lets say, 25 microseconds. I haven't found any time delay block either. So every time the input state changes I need to increase the counter and give a short pulse to the same output.5 Replies
Altera_ForumHere's the code for counter that works fine. It resets the counter when reset goes from 0 to 1.
always @(posedge clk) begin if (reset) begin if (!oldReset) begin[/INDENT] count <= 0;[/INDENT][/INDENT] end[/INDENT] oldReset <= 1;[/INDENT] //increase counter[/INDENT] if (count_enable) begin[/INDENT] count <= count+1;[/INDENT][/INDENT] end[/INDENT] end else begin oldReset <= 0;[/INDENT] //increase counter[/INDENT] if (count_enable) begin[/INDENT] count <= count+1;[/INDENT][/INDENT] end[/INDENT] end end And here's the code for holding: always @ (posedge clk) begin if (in_pulse) begin counter <= 0; out_pulse <= 1;[/INDENT] end else begin counter <= counter +1; if (counter > 1250) begin[/INDENT] out_pulse <= 0; if (counter > 1000000000) begin[/INDENT][/INDENT] counter <= 1250;[/INDENT][/INDENT][/INDENT] end[/INDENT][/INDENT] end[/INDENT] else begin[/INDENT] out_pulse <= 1;[/INDENT][/INDENT] end[/INDENT] end end- Altera_Forum
The last version is basically correct. You should also review the HDL templates available in Quartus editor context menu.
I did'nt exactly understand your reset problem. The reset as shown is an asynchronous, level sensitive reset, don't be confused by the posedge keyword in this regard, it's required Verilog syntax but doesn't actually mean an edge. An asynchronous reset can be level sensitive only. The counter flip-flops can have only one clock input, that's the same situation as with any hardware counter IC. Alternatively, you can have a synchronous reset that is operating in conjunction with clock input. - Altera_Forum
Another problem is in a counter I wrote. I works fine but how do I reset it with posedge reset?
I would like to write something like this but Quartus doesn't allow it: always @ (posedge reset) begin count <= 0: end always @ (posedge increaseCounter) begin count <= count + 1; end The way I have it now is presented below: always @ (posedge inc_counter or posedge reset) begin if (reset) begin count <= 16'b0000_0000_0000_0000; end else begin count <= count + 1'b1; end[/INDENT] end The problem is that reset keeps its value 1 and I don't want to reset counter then but only @ posedge reset. I remember I read somewhere how to check which posedge is the actual trigger but I couldn't find it again. - Altera_Forum
Okey, I have been studying Verilog and I managed to write what I wanted but I still can't build a timer. I've tried e.g.
always @ (posedge pulse_in) begin pulse_out = 1; repeat (5) begin @ (posedge clk) ; end pulse_out = 0; [/INDENT] end but Quartus doesn't allow this (multiple event control statements not supported for synthesis). So what would be a solution? - Altera_Forum
Basically you need a clock to generate the delay, possibly debounce the input, easy detect edges on mutiple inputs. If the timing isn't critical, also the internal clock oscillator of a MAX II CPLD can be used, with FPGA, you very likely have a crystal oscillator available on your board.
