From f55d4cc2fd0176021257cbc120bc68c5eaf6106f Mon Sep 17 00:00:00 2001
From: Andrew Zonenberg <azonenberg@drawersteak.com>
Date: Sat, 5 Aug 2017 17:33:44 -0700
Subject: [PATCH] Improved cells_sim_digital model for GP_COUNT8

---
 techlibs/greenpak4/cells_sim.v         | 39 -------------
 techlibs/greenpak4/cells_sim_digital.v | 76 +++++++++++++++++++++++++-
 2 files changed, 75 insertions(+), 40 deletions(-)

diff --git a/techlibs/greenpak4/cells_sim.v b/techlibs/greenpak4/cells_sim.v
index fe11d701e..13d7d19df 100644
--- a/techlibs/greenpak4/cells_sim.v
+++ b/techlibs/greenpak4/cells_sim.v
@@ -5,45 +5,6 @@
 
 //Cells still in this file have INCOMPLETE simulation models, need to finish them
 
-module GP_COUNT8(input CLK, input wire RST, output reg OUT, output reg[7:0] POUT);
-
-	parameter RESET_MODE 	= "RISING";
-
-	parameter COUNT_TO		= 8'h1;
-	parameter CLKIN_DIVIDE	= 1;
-
-	//more complex hard IP blocks are not supported for simulation yet
-
-	reg[7:0] count = COUNT_TO;
-
-	//Combinatorially output whenever we wrap low
-	always @(*) begin
-		OUT <= (count == 8'h0);
-		OUT <= count;
-	end
-
-	//POR or SYSRST reset value is COUNT_TO. Datasheet is unclear but conversations w/ Silego confirm.
-	//Runtime reset value is clearly 0 except in count/FSM cells where it's configurable but we leave at 0 for now.
-	//Datasheet seems to indicate that reset is asynchronous, but for now we model as sync due to Yosys issues...
-	always @(posedge CLK) begin
-
-		count		<= count - 1'd1;
-
-		if(count == 0)
-			count	<= COUNT_TO;
-
-		/*
-		if((RESET_MODE == "RISING") && RST)
-			count	<= 0;
-		if((RESET_MODE == "FALLING") && !RST)
-			count	<= 0;
-		if((RESET_MODE == "BOTH") && RST)
-			count	<= 0;
-		*/
-	end
-
-endmodule
-
 module GP_COUNT14(input CLK, input wire RST, output reg OUT);
 
 	parameter RESET_MODE 	= "RISING";
diff --git a/techlibs/greenpak4/cells_sim_digital.v b/techlibs/greenpak4/cells_sim_digital.v
index cf80cece0..db5bd9112 100644
--- a/techlibs/greenpak4/cells_sim_digital.v
+++ b/techlibs/greenpak4/cells_sim_digital.v
@@ -15,7 +15,13 @@ module GP_3LUT(input IN0, IN1, IN2, output OUT);
 	assign OUT = INIT[{IN2, IN1, IN0}];
 endmodule
 
-module GP_4LUT(input IN0, IN1, IN2, IN3, output OUT);
+module GP_4LUT(
+	input wire IN0,
+	input wire IN1,
+	input wire IN2,
+	input wire IN3,
+	output wire OUT);
+
 	parameter [15:0] INIT = 0;
 	assign OUT = INIT[{IN3, IN2, IN1, IN0}];
 endmodule
@@ -24,6 +30,74 @@ module GP_CLKBUF(input wire IN, output wire OUT);
 	assign OUT = IN;
 endmodule
 
+module GP_COUNT8(
+	input wire CLK,
+	input wire RST,
+	output reg OUT,
+	output reg[7:0] POUT);
+
+	parameter RESET_MODE 	= "RISING";
+
+	parameter COUNT_TO		= 8'h1;
+	parameter CLKIN_DIVIDE	= 1;
+
+	reg[7:0] count = COUNT_TO;
+
+	//Combinatorially output underflow flag whenever we wrap low
+	always @(*) begin
+		OUT <= (count == 8'h0);
+		OUT <= count;
+	end
+
+	//POR or SYSRST reset value is COUNT_TO. Datasheet is unclear but conversations w/ Silego confirm.
+	//Runtime reset value is clearly 0 except in count/FSM cells where it's configurable but we leave at 0 for now.
+	generate
+		case(RESET_MODE)
+
+			"RISING": begin
+				always @(posedge CLK or posedge RST) begin
+					count		<= count - 1'd1;
+					if(count == 0)
+						count	<= COUNT_TO;
+
+					if(RST)
+						count	<= COUNT_0;
+				end
+			end
+
+			"FALLING": begin
+				always @(posedge CLK or negedge RST) begin
+					count		<= count - 1'd1;
+					if(count == 0)
+						count	<= COUNT_TO;
+
+					if(!RST)
+						count	<= COUNT_0;
+				end
+			end
+
+			"BOTH": begin
+				initial begin
+					$display("Both-edge reset mode for GP_COUNT8 not implemented");
+					$finish;
+				end
+			end
+
+			"LEVEL": begin
+			end
+
+			default: begin
+				initial begin
+					$display("Invalid RESET_MODE on GP_COUNT8");
+					$finish;
+				end
+			end
+
+		endcase
+	endgenerate
+
+endmodule
+
 module GP_DCMPREF(output reg[7:0]OUT);
 	parameter[7:0] REF_VAL = 8'h00;
 	initial OUT = REF_VAL;
-- 
2.30.2