From 31fd1ded97e89e047dc7f032d8bab22fe56a92d2 Mon Sep 17 00:00:00 2001
From: Peter McGoron <code@mcgoron.com>
Date: Sun, 23 Oct 2022 04:56:56 -0400
Subject: [PATCH] factor out code

---
 spi_master.v             | 32 +++++++++++++++++++-------------
 spi_master_ss_template.v | 17 ++++++++++++++---
 tests/mk.sh              | 31 ++++++++++++++++---------------
 tests/simtop.v           |  3 ++-
 4 files changed, 51 insertions(+), 32 deletions(-)

diff --git a/spi_master.v b/spi_master.v
index d8b9020..d6018c0 100644
--- a/spi_master.v
+++ b/spi_master.v
@@ -18,9 +18,8 @@ spi_master
 #(
 	parameter WID = 24, // Width of bits per transaction.
 	parameter WID_LEN = 5, // Length in bits required to store WID
-	parameter CYCLE_HALF_WAIT = 1, // One less than half of the wait time of a cycle.
-	                               // One cycle of a transfer is 2(CYCLE_HALF_WAIT + 1)
-	                               // clock cycles.
+	parameter CYCLE_HALF_WAIT = 1, // Half of the wait time of a cycle minus 1.
+	                               // One SCK cycle is 2*(CYCLE_HALF_WAIT + 1) clock cycles.
 	parameter TIMER_LEN = 3, // Length in bits required to store CYCLE_HALF_WAIT
 	parameter POLARITY = 0, // 0 = sck idle low, 1 = sck idle high
 	parameter PHASE = 0 // 0 = rising-read falling-write, 1 = rising-write falling-read.
@@ -104,6 +103,16 @@ task setup_bits();
 	end
 endtask
 
+task cycle_change();
+	// Stop transfer when the clock returns to its original polarity.
+	if (bit_counter == WID[WID_LEN-1:0] && sck == POLARITY[0]) begin
+		state <= WAIT_FINISHED;
+	end else begin
+		sck <= !sck;
+		state <= ON_CYCLE;
+	end
+endtask
+
 always @ (posedge clk) begin
 	case (state)
 	WAIT_ON_ARM: begin
@@ -137,19 +146,16 @@ always @ (posedge clk) begin
 			end
 		end
 
-		state <= CYCLE_WAIT;
+		if (CYCLE_HALF_WAIT == 0) begin
+			cycle_change();
+		end else begin
+			state <= CYCLE_WAIT;
+		end
 	end
 	CYCLE_WAIT: begin
 		if (timer == CYCLE_HALF_WAIT) begin
-			timer <= 0;
-			// Stop transfer when the clock returns
-			// to its original polarity.
-			if (bit_counter == WID[WID_LEN-1:0] && sck == POLARITY[0]) begin
-				state <= WAIT_FINISHED;
-			end else begin
-				state <= ON_CYCLE;
-				sck <= !sck;
-			end
+			timer <= 1;
+			cycle_change();
 		end else begin
 			timer <= timer + 1;
 		end
diff --git a/spi_master_ss_template.v b/spi_master_ss_template.v
index eeaf01c..27a4b85 100644
--- a/spi_master_ss_template.v
+++ b/spi_master_ss_template.v
@@ -63,19 +63,30 @@ localparam WAIT_ON_MASTER = 2;
 localparam WAIT_ON_ARM_DEASSERT = 3;
 reg [2:0] state = WAIT_ON_ARM;
 
+task master_arm();
+	arm_master <= 1;
+	state <= WAIT_ON_MASTER;
+endtask
+
 always @ (posedge clk) begin
 	case (state)
 	WAIT_ON_ARM: begin
 		if (arm) begin
 			timer <= 1;
-			state <= WAIT_ON_SS;
+			if (SS_WAIT == 0) begin
+				master_arm();
+			end else begin
+				timer <= 1;
+				state <= WAIT_ON_SS;
+			end
 			ss <= 1;
 		end
 	end
 	WAIT_ON_SS: begin
 		if (timer == SS_WAIT) begin
-			arm_master <= 1;
-			state <= WAIT_ON_MASTER;
+			master_arm();
+		end else begin
+			timer <= timer + 1;
 		end
 	end
 	WAIT_ON_MASTER: begin
diff --git a/tests/mk.sh b/tests/mk.sh
index f907668..51a9775 100755
--- a/tests/mk.sh
+++ b/tests/mk.sh
@@ -16,6 +16,7 @@ run_test() {
 		-GPOLARITY=$POL -GPHASE=$PHASE -GWID=$WID -CFLAGS -DWID=$WID \
 		-GWID_LEN=$WIDLEN \
 		-DSPI_MASTER_TYPE=$MASTER_TYPE -DSPI_SLAVE_TYPE=$SLAVE_TYPE \
+		-DVCDFILE="\"$DIR.vcd\"" \
 		--Mdir $DIR \
 		$EXTARG \
 		simtop.v write_read.cpp $MODS
@@ -34,21 +35,21 @@ for POL in 0 1; do
 			"../spi_master.v ../spi_slave.v"
 		)
 
-		( \
-			run_test $POL $PHASE \
-			spi_master_no_write spi_slave_no_read \
-			simtop_no_write_$POL$PHASE 24 \
-			"../spi_master_no_write.v ../spi_slave_no_read.v" \
-			"-DSPI_MASTER_NO_WRITE -CFLAGS -DSPI_MASTER_NO_WRITE"
-		)
-
-		( \
-			run_test $POL $PHASE \
-			spi_master_no_read spi_slave_no_write \
-			simtop_no_read_$POL$PHASE 24 \
-			"../spi_master_no_read.v ../spi_slave_no_write.v" \
-			"-DSPI_MASTER_NO_READ -CFLAGS -DSPI_MASTER_NO_READ"
-		)
+#		( \
+#			run_test $POL $PHASE \
+#			spi_master_no_write spi_slave_no_read \
+#			simtop_no_write_$POL$PHASE 24 \
+#			"../spi_master_no_write.v ../spi_slave_no_read.v" \
+#			"-DSPI_MASTER_NO_WRITE -CFLAGS -DSPI_MASTER_NO_WRITE"
+#		)
+#
+#		( \
+#			run_test $POL $PHASE \
+#			spi_master_no_read spi_slave_no_write \
+#			simtop_no_read_$POL$PHASE 24 \
+#			"../spi_master_no_read.v ../spi_slave_no_write.v" \
+#			"-DSPI_MASTER_NO_READ -CFLAGS -DSPI_MASTER_NO_READ"
+#		)
 
 	done
 done
diff --git a/tests/simtop.v b/tests/simtop.v
index 91533fd..d47a802 100644
--- a/tests/simtop.v
+++ b/tests/simtop.v
@@ -46,7 +46,8 @@ reg slave_error;
 	.POLARITY(POLARITY),
 	.PHASE(PHASE),
 	.WID(WID),
-	.WID_LEN(WID_LEN)
+	.WID_LEN(WID_LEN),
+	.CYCLE_HALF_WAIT(5)
 ) master (
 	.clk(clk),
 `ifndef SPI_MASTER_NO_WRITE