From 2b73796a5c0f341129d68d59bc19947c132dd8fe Mon Sep 17 00:00:00 2001
From: Greg Savin <43152568+SiFiveGregS@users.noreply.github.com>
Date: Thu, 28 Mar 2019 09:48:22 -0700
Subject: Adjusted epilogue width.

---
 src/jtag/drivers/ftdi.c                   | 80 +++++++++++++++++--------------
 tcl/board/sifive-e31arty-onboard-ftdi.cfg |  4 +-
 2 files changed, 47 insertions(+), 37 deletions(-)

diff --git a/src/jtag/drivers/ftdi.c b/src/jtag/drivers/ftdi.c
index 7b25190..48150c2 100644
--- a/src/jtag/drivers/ftdi.c
+++ b/src/jtag/drivers/ftdi.c
@@ -504,39 +504,49 @@ static void ftdi_execute_pathmove(struct jtag_command *cmd)
 }
 
 #if BUILD_FTDI_BSCAN == 1
-static void bscan_single_field_data_scan(const uint8_t *out, unsigned out_offset, uint8_t *in,
+static void bscan_shift(bool traverse_to_end_state, const uint8_t *out, unsigned out_offset, uint8_t *in,
 				    unsigned in_offset, unsigned length)
 {
-	DO_CLOCK_DATA(mpsse_ctx,
-		      out,
-		      0,
-		      in,
-		      0,
-		      length - 1,
-		      ftdi_jtag_mode);
-	uint8_t last_bit = 0;
-	if (out)
-		bit_copy(&last_bit, 0, out, length - 1, 1);
-	uint8_t tms_bits = 0x01;
-	DO_CLOCK_TMS_CS(mpsse_ctx,
-			&tms_bits,
-			0,
-			in,
-			length - 1,
-			1,
-			last_bit,
-			ftdi_jtag_mode);
-	tap_set_state(tap_state_transition(tap_get_state(), 1));
-	DO_CLOCK_TMS_CS_OUT(mpsse_ctx,
-			    &tms_bits,
-			    1,
-			    1,
-			    last_bit,
-			    ftdi_jtag_mode);
-	tap_set_state(tap_state_transition(tap_get_state(), 0));
-
-	if (tap_get_state() != tap_get_end_state())
-		move_to_state(tap_get_end_state());
+	if (traverse_to_end_state) {
+		DO_CLOCK_DATA(mpsse_ctx,
+			      out,
+			      out_offset,
+			      in,
+			      in_offset,
+			      length - 1,
+			      ftdi_jtag_mode);
+		uint8_t last_bit = 0;
+		if (out)
+			bit_copy(&last_bit, 0, out, length - 1, 1);
+		uint8_t tms_bits = 0x01;
+		DO_CLOCK_TMS_CS(mpsse_ctx,
+				&tms_bits,
+				0,
+				in,
+				in_offset + length - 1,
+				1,
+				last_bit,
+				ftdi_jtag_mode);
+		tap_set_state(tap_state_transition(tap_get_state(), 1));
+		DO_CLOCK_TMS_CS_OUT(mpsse_ctx,
+				    &tms_bits,
+				    1,
+				    1,
+				    0,
+				    ftdi_jtag_mode);
+		tap_set_state(tap_state_transition(tap_get_state(), 0));
+
+		if (tap_get_state() != tap_get_end_state())
+			move_to_state(tap_get_end_state());
+	} else {
+		DO_CLOCK_DATA(mpsse_ctx,
+			      out,
+			      out_offset,
+			      in,
+			      in_offset,
+			      length,
+			      ftdi_jtag_mode);
+	}		
 }
 
 
@@ -566,7 +576,7 @@ static void ftdi_execute_scan_via_bscan(struct jtag_command *cmd)
 		
 	// Do the 6-bit IR scan of 0x23 (USER4)
 
-	bscan_single_field_data_scan(&bscan_ir_user, 0, NULL, 0, bscan_ir_user_width);
+	bscan_shift(true, &bscan_ir_user, 0, NULL, 0, bscan_ir_user_width);
 		
 	if (tap_get_state() != tap_get_end_state())
 		move_to_state(tap_get_end_state());
@@ -584,7 +594,7 @@ static void ftdi_execute_scan_via_bscan(struct jtag_command *cmd)
 
 	// shift in prologue
 	uint8_t prologue = (scan_size << 1) | (cmd->cmd.scan->ir_scan ? 0 : 1);
-	static const uint8_t epilogue = 0x1;
+	static const uint8_t epilogue = 0x0;
 	
 	DO_CLOCK_DATA(mpsse_ctx,
 		      &prologue,
@@ -639,8 +649,8 @@ static void ftdi_execute_scan_via_bscan(struct jtag_command *cmd)
 			      ftdi_jtag_mode);
 	
 
-	// shift in epilogue and exit shift state
-	bscan_single_field_data_scan(&epilogue, 0, NULL, 0, 2);	
+	// shift in epilogue (3 bits of value zero), exiting shift state and traversing to idle state
+	bscan_shift(true, &epilogue, 0, NULL, 0, 3);	
 
 	if (tap_get_state() != tap_get_end_state())
 		move_to_state(tap_get_end_state());
diff --git a/tcl/board/sifive-e31arty-onboard-ftdi.cfg b/tcl/board/sifive-e31arty-onboard-ftdi.cfg
index c36e6f1..745828a 100644
--- a/tcl/board/sifive-e31arty-onboard-ftdi.cfg
+++ b/tcl/board/sifive-e31arty-onboard-ftdi.cfg
@@ -4,9 +4,9 @@
 # -c "adapter_khz 5000" -f "interface/ftdi/arty-onboard-ftdi.cfg" -f "board/sifive-e31arty-onboard-ftdi.cfg"
 
 set _CHIPNAME riscv
-jtag newtap $_CHIPNAME cpu -irlen 6 -expected-id 0x0362d093
+jtag newtap $_CHIPNAME cpu -irlen 6; # -expected-id 0x0362d093
 
-# Arrange for bscan tunneling mode to become active after the JTAG chain is verified
+# Arrange for bscan tunneling mode to become active after the JTAG chain is verified (or has been reset but even if the full verification sequence wasn't perfect)
 jtag configure $_CHIPNAME.cpu -event setup {
   ftdi_bscan_mode on
 }
-- 
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