adc_mic_lcd demonstration on NEEK max10

Altera_Forum · ‎03-14-2018

im looking at the code, from terasic max10 neek demonstration files.

and trying to understand what purpose it serves:

module  MAX10_ADC   (  
 input  SYS_CLK ,
 input  SYNC_TR,
 input  RESET_n ,
 input  ADC_CH ,
 output reg DATA ,
 output DATA_VALID,
 input  FITER_EN 
 );
wire sys_clk;
wire        response_valid;
wire        command_startofpacket;
wire        command_endofpacket;
wire        command_ready;
wire   response_channel;
wire  response_data;
wire        response_startofpacket;
wire        response_endofpacket;
reg    cur_adc_ch;
reg   adc_sample_data;
assign DATA_VALID  =response_valid;
// continused send command
assign command_startofpacket  = 1'b1;    // ignore in altera_adc_control core
assign command_endofpacket    = 1'b1;      // ignore in altera_adc_control core
// --adc_sample_data: hold 12-bit adc sample value
// --max10 adc chanel    
adc_qsys u0 (
        .clk_clk                              (SYS_CLK ) ,// ADC_CLK_10),
        .reset_reset_n                        (RESET_n),   
        .modular_adc_0_command_valid          (SYNC_TR),          
        .modular_adc_0_command_channel        (ADC_CH),        //                       .channel
        .modular_adc_0_command_startofpacket  (command_startofpacket),  //                       .startofpacket
        .modular_adc_0_command_endofpacket    (command_endofpacket),    //                       .endofpacket
        .modular_adc_0_command_ready          (command_ready),          //                       .ready
        .modular_adc_0_response_valid         (response_valid        ),         // modular_adc_0_response.valid
        .modular_adc_0_response_channel       (response_channel      ),       //                       .channel
        .modular_adc_0_response_data          (response_data         ),          //                       .data
        .modular_adc_0_response_startofpacket (response_startofpacket),   //                       .startofpacket
        .modular_adc_0_response_endofpacket   (response_endofpacket),     //                       .endofpacket
        .clock_bridge_sys_out_clk_clk         (sys_clk)                  
    );
//--data latch 
reg response_valid_r ; 
reg  ADC_RD0,ADC_RD1,ADC_RD2,ADC_RD3,ADC_RD4,ADC_RD5 ; 
reg   CNT ;
always @ ( posedge sys_clk )
begin
   response_valid_r  <= response_valid ; 
    if (~response_valid_r  &  response_valid)
    begin
          { ADC_RD0,ADC_RD1,ADC_RD2,ADC_RD3,ADC_RD4,ADC_RD5 } <= { ADC_RD1,ADC_RD2,ADC_RD3,ADC_RD4, ADC_RD5,response_data };
            DATA  <= FITER_EN ? (ADC_RD0+ADC_RD1+ADC_RD2+ADC_RD3+ADC_RD4+ADC_RD5)/6  : response_data ;//response_data;        
    end
end            
endmodule

im trying to figure out what the last paragraph is doing

from my understanding

always @ ( posedge sys_clk )
begin
   response_valid_r  <= response_valid ; 
    if (~response_valid_r  &  response_valid)
    begin
          { ADC_RD0,ADC_RD1,ADC_RD2,ADC_RD3,ADC_RD4,ADC_RD5 } <= { ADC_RD1,ADC_RD2,ADC_RD3,ADC_RD4, ADC_RD5,response_data };
            DATA  <= FITER_EN ? (ADC_RD0+ADC_RD1+ADC_RD2+ADC_RD3+ADC_RD4+ADC_RD5)/6  : response_data ;//response_data;        
    end
end

the if statement is never successbecause the if is always '0'.

thanks.

Altera_Forum · ‎03-15-2018

I've found there's quite a large amount of Terasic's 'reference' code that could do with some attention - although this isn't that bad...

Don't be fooled by the fact that the line of code updating 'response_valid_r' might appear to be immediately before it is tested. You could put the statement updating 'response_valid_r' after the if statement and realise the same behaviour. Both statements are evaluated on each rising edge of the clock. The test where the conditional statement is true will be when 'response_valid_r' is low and 'response_valid' has gone high, the clock cycle before 'response_valid_r' has been updated (high).

Ultimately, it's looking for a rising edge on 'response_valid'. Thus you end up with a single clock cycle where the 'if' statement is true.

If in doubt, simulate that little block of code.

Cheers,

Alex