Defying Gravity - A Minimal Cognitive Sensorimotor Loop Which Makes Robots With Arbitrary Morphologies Stand Up からの引用

CSL.v

reg [17:0] voltage;
reg [16:0] timer;
always @(posedge ADC_CLK)
case (state)
	0 : begin // sense ----------------------------------- 
		if (ADC_DAT == 1) 
			begin
				if ($signed(voltage) < $signed(18'h1FFFF))
		    			voltage <= voltage + 1; // if not saturated
			end 
		else if ($signed(voltage) > $signed(18'b20001))
	    		voltage <= voltage - 1; // if not saturated

		timer <= timer - 1;

		if (timer == 0) 
	    		begin // end of sense-phase
	        		{MOT_A, MOT_B} <= {~voltage[17], voltage[17]};
	        		if (&voltage[17:13] | ~|voltage[17:13])
	        			timer <= 0; // below min. voltage
	           		else
	           			timer <= voltage[17:1];
	           		state <= 1; // switch to drive-phase
			end 
	end
	1 : begin // drive ----------------------------------- 
		if (timer[16])
			timer <= timer + 1; // count up to zero
		else
	        	timer <= timer - 1; // count down to zero
		if (timer == 0) 
	    		begin // end of drive-phase
	        		timer <= 17'd99999; // prepare T = 10ms
	        		{MOT_A, MOT_B} <= 2'b11; // float motor outputs
	            		state <= 0; // switch to sense-phase
			end 
	end
endcase

http://www.neurorobotik.de/downloads/publications/2013%20Hild%20-%20Defying%20Gravity.pdf