Various tweaks to Dac test case. Updated documentation to reflect that inference of parallel counter outputs to DACs is now supported

azonenberg · azonenberg · commit 7899229df9f9 · 2017-05-22T19:44:37.000-07:00
diff --git a/doc/gp4-hdl.tex b/doc/gp4-hdl.tex
@@ -806,9 +806,9 @@ \subsection{Counters}
 \namestyle{Yosys} provides limited inference capability for counters which match the capabilities of the hard macro counters
 (\tokenref{GP\_COUNT8}{gp-count8} and \tokenref{GP\_COUNT14}{gp-count14}) in the device.
 
-Some hard macro capabilities (most notably input dividers and parallel output to DCMP/DAC blocks) are not yet supported
-for inference; if these capabilities are required then use explicit primitive instantiation. Future software releases
-will expand the set of counter features which may be inferred.
+Some hard macro capabilities (most notably input dividers) are not yet supported for inference; if these capabilities
+are required then use explicit primitive instantiation. Future software releases will expand the set of counter
+features which may be inferred.
 
 \subsubsection{Inference Requirements}
 
@@ -819,8 +819,6 @@ \subsubsection{Inference Requirements}
 \item Count down only
 \item Be initialized to the same (maximum) value by both underflow and by power-on reset
 \item Have either no reset, or a positive level triggered reset to zero
-\item Not have any logic use the internal counter register. Only the ``underflow" signal may be used by surrounding
-logic.
 \end{itemize}
 
 \subsubsection{Counter Related Constraints}
diff --git a/tests/greenpak4/CMakeLists.txt b/tests/greenpak4/CMakeLists.txt
@@ -24,7 +24,8 @@ function(add_greenpak4_netlist name part)
 
 	add_custom_command(
 		OUTPUT  "${CMAKE_CURRENT_BINARY_DIR}/${name}.json"
-		COMMAND "${YOSYS_COMMAND}" -q
+		COMMAND "${YOSYS_COMMAND}"
+				-q
 				-p "read_verilog ${CMAKE_CURRENT_SOURCE_DIR}/${name}.v"
 				-p "synth_greenpak4 -top ${name} -part ${part}"
 				-p "write_json   ${CMAKE_CURRENT_BINARY_DIR}/${name}.json"
diff --git a/tests/greenpak4/slg46620v/Dac.v b/tests/greenpak4/slg46620v/Dac.v
@@ -98,10 +98,7 @@ module Dac(bg_ok, vout, vout2, wave_sync);
 
 	localparam COUNT_MAX = 255;
 
-	//TODO: support for inference of counters with parallel output
-	/*
-	(* LOC = "COUNT8_6" *)
-	(* COUNT_EXTRACT = "FORCE" *)
+	//Inferred counter that drives both the DAC and an overflow output
 	reg[7:0] count = COUNT_MAX;
 	always @(posedge clk_1730hz) begin
 		if(count == 0)
@@ -112,32 +109,19 @@ module Dac(bg_ok, vout, vout2, wave_sync);
 
 	//Counter overflow signal to LED
 	assign wave_sync = (count == 0);
-	*/
-
-	//Explicitly instantiated counter b/c we don't yet have inference support when using POUT
-	wire[7:0] count_pout;
-	GP_COUNT8 #(
-		.CLKIN_DIVIDE(1),
-		.COUNT_TO(COUNT_MAX),
-		.RESET_MODE("RISING")
-	) cnt (
-		.CLK(clk_1730hz),
-		.RST(1'b0),
-		.OUT(wave_sync),
-		.POUT(count_pout)
-	);
 
 	////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
-	// DAC driving the voltage reference
+	// The DACs
 
-	wire vdac;
+	//This one drives a top-level output pin directly (GP_VREF and GP_ACMP are infrred)
 	(* LOC = "DAC_1" *)
 	GP_DAC dac(
-		.DIN(count_pout),
-		.VOUT(vdac),
+		.DIN(count),
+		.VOUT(vout),
 		.VREF(vref_1v0)
 	);
 
+	//This one drives a GP_VREF explicitly (GP_ACMP is inferred)
 	wire vdac2;
 	(* LOC = "DAC_0" *)
 	GP_DAC dac2(
@@ -146,21 +130,15 @@ module Dac(bg_ok, vout, vout2, wave_sync);
 		.VREF(vref_1v0)
 	);
 
-	////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
-	// Drive one pin with the DAC output directly, no vref
-
-	//assign vout = vdac;
-	assign vout2 = vdac2;
-
 	////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
 	// Drive the other via a buffered reference
 
 	GP_VREF #(
 		.VIN_DIV(4'd1),
 		.VREF(16'd00)
 	) vrdac (
-		.VIN(vdac),
-		.VOUT(vout)
+		.VIN(vdac2),
+		.VOUT(vout2)
 	);
 
 
