diff --git a/README b/README
index ebb4bb6..c9fe2ac 100644
--- a/README
+++ b/README
@@ -63,8 +63,8 @@ Design Principles
 TODO (as of January, 2013)
 
 short-term (1 month):
+* support distributed and block memory
 * example: counter (including clock, jtag)
-* support xc6slx9-ftg256
 
 mid-term (6 months):
 * example: j1 soc
diff --git a/autotest.c b/autotest.c
index f6d65c9..4540561 100644
--- a/autotest.c
+++ b/autotest.c
@@ -1795,8 +1795,27 @@ static int test_dcm_config(struct test_state* tstate)
 
 static int test_bscan_config(struct test_state* tstate)
 {
-// todo: not implemented
+	int bscan_y, bscan_x, bscan_type_idx, enum_i, rc;
+	int jtag_chain_i, jtag_test;
+
+	enum_i = 0;
+	while (!(rc = fdev_enum(tstate->model, DEV_BSCAN, enum_i++, &bscan_y,
+			&bscan_x, &bscan_type_idx)) && bscan_y != -1) {
+		for (jtag_chain_i = 1; jtag_chain_i <= 4; jtag_chain_i++) {
+			for (jtag_test = 0; jtag_test <= 1; jtag_test++) {
+				rc = fdev_bscan(tstate->model, bscan_y, bscan_x, bscan_type_idx,
+					jtag_chain_i, jtag_test ? BSCAN_JTAG_TEST_Y : BSCAN_JTAG_TEST_N);
+				if (rc) FAIL(rc);
+				if ((rc = diff_printf(tstate))) FAIL(rc);
+				fdev_delete(tstate->model, bscan_y, bscan_x, DEV_BSCAN, bscan_type_idx);
+				if ((rc = diff_printf(tstate))) FAIL(rc);
+			}
+		}
+	}
+	if (rc) FAIL(rc);
 	return 0;
+fail:
+	return rc;
 }
 
 static int test_clock_routing(struct test_state* tstate)
diff --git a/libs/bit_frames.c b/libs/bit_frames.c
index cd43268..4406f1e 100644
--- a/libs/bit_frames.c
+++ b/libs/bit_frames.c
@@ -2217,6 +2217,80 @@ static void destruct_extract_state(struct extract_state *es)
 	es->yx_pos = 0;
 }
 
+static int extract_bscan(struct extract_state *es)
+{
+	int enum_i, bscan_y, bscan_x, bscan_type_idx;
+	int jtag_chain, jtag_test, pinword;
+	uint8_t *u8_p;
+	struct fpga_device *dev;
+
+	RC_CHECK(es->model);
+	enum_i = 0;
+	while (!fdev_enum(es->model, DEV_BSCAN, enum_i++, &bscan_y,
+			&bscan_x, &bscan_type_idx) && bscan_y != -1) {
+
+		u8_p = get_first_minor(es->bits, which_row(bscan_y, es->model), es->model->x_major[bscan_x]);
+		RC_ASSERT(es->model, u8_p);
+		pinword = frame_get_pinword(u8_p + XC6_BSCAN_MINOR*FRAME_SIZE + XC6_BSCAN_WORD*XC6_WORD_BYTES);
+
+		if (!(pinword & (1 << ((bscan_y - TOP_IO_TILES)*2 + bscan_type_idx))))
+			continue;
+		pinword &= ~(1 << ((bscan_y - TOP_IO_TILES)*2 + bscan_type_idx));
+
+		jtag_chain = 1;
+		jtag_test = BSCAN_JTAG_TEST_N;
+		if (bscan_y == TOP_IO_TILES && !bscan_type_idx
+		    && (pinword & (1 << XC6_BSCAN_TEST_PIN))) {
+			pinword &= ~(1 << XC6_BSCAN_TEST_PIN);
+			jtag_test = BSCAN_JTAG_TEST_Y;
+		}
+
+		if (pinword) {
+			HERE();
+			continue;
+		}
+		dev = fdev_p(es->model, bscan_y, bscan_x, DEV_BSCAN, bscan_type_idx);
+		RC_ASSERT(es->model, dev);
+		if (dev->instantiated) {
+			HERE();
+			continue;
+		}
+		fdev_bscan(es->model, bscan_y, bscan_x, bscan_type_idx,
+			jtag_chain, jtag_test);
+		RC_CHECK(es->model);
+		frame_set_pinword(u8_p + XC6_BSCAN_MINOR*FRAME_SIZE + XC6_BSCAN_WORD*XC6_WORD_BYTES, 0);
+	}
+	RC_RETURN(es->model);
+}
+
+static int write_bscan(struct fpga_bits *bits, struct fpga_model *model)
+{
+	int enum_i, bscan_y, bscan_x, bscan_type_idx, pinword;
+	struct fpga_device *dev;
+	uint8_t *u8_p;
+
+	RC_CHECK(model);
+	enum_i = 0;
+	while (!fdev_enum(model, DEV_BSCAN, enum_i++, &bscan_y,
+			&bscan_x, &bscan_type_idx) && bscan_y != -1) {
+		dev = fdev_p(model, bscan_y, bscan_x, DEV_BSCAN, bscan_type_idx);
+		RC_ASSERT(model, dev);
+		if (!dev->instantiated) continue;
+
+		u8_p = get_first_minor(bits, which_row(bscan_y, model), model->x_major[bscan_x]);
+		RC_ASSERT(model, u8_p);
+		pinword = frame_get_pinword(u8_p + XC6_BSCAN_MINOR*FRAME_SIZE + XC6_BSCAN_WORD*XC6_WORD_BYTES);
+
+		if (bscan_y == TOP_IO_TILES && !bscan_type_idx
+		    && dev->u.bscan.jtag_test == BSCAN_JTAG_TEST_Y)
+			pinword |= 1 << XC6_BSCAN_TEST_PIN;
+		pinword |= 1 << ((bscan_y - TOP_IO_TILES)*2 + bscan_type_idx);
+
+		frame_set_pinword(u8_p + XC6_BSCAN_MINOR*FRAME_SIZE + XC6_BSCAN_WORD*XC6_WORD_BYTES, pinword);
+	}
+	RC_RETURN(model);
+}
+
 int extract_model(struct fpga_model* model, struct fpga_bits* bits)
 {
 	struct extract_state es;
@@ -2241,6 +2315,8 @@ int extract_model(struct fpga_model* model, struct fpga_bits* bits)
 	if (rc) { RC_SET(model, rc); goto out; }
 	rc = extract_logic(&es);
 	if (rc) { RC_SET(model, rc); goto out; }
+	rc = extract_bscan(&es);
+	if (rc) { RC_SET(model, rc); goto out; }
 
 	// turn switches into nets
 	if (model->nets)
@@ -3042,7 +3118,7 @@ static int write_logic(struct fpga_bits* bits, struct fpga_model* model)
 	RC_RETURN(model);
 }
 
-int write_model(struct fpga_bits* bits, struct fpga_model* model)
+int write_model(struct fpga_bits *bits, struct fpga_model *model)
 {
 	int i;
 
@@ -3053,6 +3129,7 @@ int write_model(struct fpga_bits* bits, struct fpga_model* model)
 	write_switches(bits, model);
 	write_type2(bits, model);
 	write_logic(bits, model);
+	write_bscan(bits, model);
 
 	RC_RETURN(model);
 }
diff --git a/libs/control.c b/libs/control.c
index 5ced012..ee8352c 100644
--- a/libs/control.c
+++ b/libs/control.c
@@ -80,21 +80,24 @@ const char *fpga_iob_sitename(struct fpga_model *model,
 static void enum_x(struct fpga_model *model, enum fpgadev_type type,
 	int enum_i, int *y, int x, int *type_idx)
 {
-	int type_count, i, _y;
+	int tile_type_count, total_type_count, i, _y;
 	struct fpga_tile* tile;
 
-	type_count = 0;
+	total_type_count = 0;
+	tile_type_count = 0;
 	for (_y = 0; _y < model->y_height; _y++) {
 		tile = YX_TILE(model, _y, x);
+		total_type_count += tile_type_count;
+		tile_type_count = 0;
 		for (i = 0; i < tile->num_devs; i++) {
 			if (tile->devs[i].type != type)
 				continue;
-			if (type_count == enum_i) {
+			if (total_type_count + tile_type_count == enum_i) {
 				*y = _y;
-				*type_idx = type_count;
+				*type_idx = tile_type_count;
 				return;
 			}
-			type_count++;
+			tile_type_count++;
 		}
 	}
 	*y = -1;
@@ -106,6 +109,7 @@ int fdev_enum(struct fpga_model* model, enum fpgadev_type type, int enum_i,
 	struct fpga_tile* tile;
 	int i, j, type_count;
 
+	*y = -1;
 	RC_CHECK(model);
 	switch (type) {
 		case DEV_BUFGMUX:
@@ -123,7 +127,6 @@ int fdev_enum(struct fpga_model* model, enum fpgadev_type type, int enum_i,
 				}
 				type_count++;
 			}
-			*y = -1;
 			RC_RETURN(model);
 		case DEV_BUFIO: {
 			int yx_pairs[] = {
@@ -147,22 +150,20 @@ int fdev_enum(struct fpga_model* model, enum fpgadev_type type, int enum_i,
 					type_count++;
 				}
 			}
-			*y = -1;
 			RC_RETURN(model);
 		}
 		case DEV_PLL:
 		case DEV_DCM:
-			enum_x(model, type, enum_i, y, model->center_x
-				- CENTER_CMTPLL_O, type_idx);
+			*x = model->center_x - CENTER_CMTPLL_O;
+			enum_x(model, type, enum_i, y, *x, type_idx);
 			RC_RETURN(model);
 		case DEV_BSCAN:
-			enum_x(model, type, enum_i, y, model->x_width
-				- RIGHT_IO_DEVS_O, type_idx);
+			*x = model->x_width - RIGHT_IO_DEVS_O;
+			enum_x(model, type, enum_i, y, *x, type_idx);
 			RC_RETURN(model);
 		default: break;
 	}
 	HERE();
-	*y = -1;
 	RC_RETURN(model);
 }
 
@@ -840,25 +841,38 @@ fail:
 	return rc;
 }
 
-int fdev_bufgmux(struct fpga_model* model, int y, int x,
+int fdev_bufgmux(struct fpga_model *model, int y, int x,
 	int type_idx, int clk, int disable_attr, int s_inv)
 {
-	struct fpga_device* dev;
+	struct fpga_device *dev;
 	int rc;
 
 	RC_CHECK(model);
 	dev = fdev_p(model, y, x, DEV_BUFGMUX, type_idx);
-	if (!dev) FAIL(EINVAL);
+	RC_ASSERT(model, dev);
 	rc = reset_required_pins(dev);
-	if (rc) FAIL(rc);
+	if (rc) RC_FAIL(model, rc);
 
 	dev->u.bufgmux.clk = clk;
 	dev->u.bufgmux.disable_attr = disable_attr;
 	dev->u.bufgmux.s_inv = s_inv;
 	dev->instantiated = 1;
-	return 0;
-fail:
-	return rc;
+	RC_RETURN(model);
+}
+
+int fdev_bscan(struct fpga_model *model, int y, int x, int type_idx,
+	int jtag_chain, int jtag_test)
+{
+	struct fpga_device *dev;
+
+	RC_CHECK(model);
+	dev = fdev_p(model, y, x, DEV_BSCAN, type_idx);
+	RC_ASSERT(model, dev);
+
+	dev->u.bscan.jtag_chain = jtag_chain;
+	dev->u.bscan.jtag_test = jtag_test;
+	dev->instantiated = 1;
+	RC_RETURN(model);
 }
 
 static void scan_lut_digits(const char* s, int* digits)
diff --git a/libs/control.h b/libs/control.h
index 6e2f6dc..b3e3730 100644
--- a/libs/control.h
+++ b/libs/control.h
@@ -103,6 +103,9 @@ int fdev_iob_drive(struct fpga_model* model, int y, int x,
 int fdev_bufgmux(struct fpga_model* model, int y, int x,
 	int type_idx, int clk, int disable_attr, int s_inv);
 
+int fdev_bscan(struct fpga_model *model, int y, int x, int type_idx,
+	int jtag_chain, int jtag_test);
+
 int fdev_set_required_pins(struct fpga_model* model, int y, int x, int type,
 	int type_idx);
 void fdev_print_required_pins(struct fpga_model* model, int y, int x,
diff --git a/libs/parts.h b/libs/parts.h
index 86ca214..c939202 100644
--- a/libs/parts.h
+++ b/libs/parts.h
@@ -450,3 +450,11 @@ void xc6_lut_bitmap(int lut_pos, int (*map)[64], int num_bits);
 
 #define XC6_TYPE2_GCLK_REG_SW	 2 // bit 2 in 1st word
 #define XC6_CENTER_GCLK_MINOR	25
+
+//
+// bscan
+//
+
+#define XC6_BSCAN_MINOR 22
+#define XC6_BSCAN_WORD 1
+#define XC6_BSCAN_TEST_PIN 4