diff --git a/bit2txt.c b/bit2txt.c
index eccfb72..f8dccff 100644
--- a/bit2txt.c
+++ b/bit2txt.c
@@ -510,11 +510,11 @@ void printf_clb(uint8_t* maj_bits, int row, int major)
 
 	// the first two slots on top and bottom row are not used for clb
 	if (!row) {
-		start = 2;
-		max_idx = 16;
-	} else if (row == 2) {
 		start = 0;
 		max_idx = 14;
+	} else if (row == 3) {
+		start = 2;
+		max_idx = 16;
 	} else {
 		start = 0;
 		max_idx = 16;
@@ -531,42 +531,50 @@ void printf_clb(uint8_t* maj_bits, int row, int major)
 
 		// LUTs
 		lut64 = read_lut64(&maj_bits[24*130], frame_off+32);
-		lut_str = lut2bool(lut64, 64);
+		{  int logic_base[6] = {0,1,0,0,1,0};
+		   lut_str = lut2bool(lut64, 64, &logic_base, 1 /* flip_b0 */); }
 		if (*lut_str)
 			printf(" s0_A6LUT \"%s\"\n", lut_str);
 
 		lut64 = read_lut64(&maj_bits[21*130], frame_off+32);
-		lut_str = lut2bool(lut64, 64);
+		{  int logic_base[6] = {1,1,0,1,0,1};
+		   lut_str = lut2bool(lut64, 64, &logic_base, 1 /* flip_b0 */); }
 		if (*lut_str)
 			printf(" s0_B6LUT \"%s\"\n", lut_str);
 
 		lut64 = read_lut64(&maj_bits[24*130], frame_off);
-		lut_str = lut2bool(lut64, 64);
+		{  int logic_base[6] = {0,1,0,0,1,0};
+		   lut_str = lut2bool(lut64, 64, &logic_base, 1 /* flip_b0 */); }
 		if (*lut_str)
 			printf(" s0_C6LUT \"%s\"\n", lut_str);
 
 		lut64 = read_lut64(&maj_bits[21*130], frame_off);
-		lut_str = lut2bool(lut64, 64);
+		{  int logic_base[6] = {1,1,0,1,0,1};
+		   lut_str = lut2bool(lut64, 64, &logic_base, 1 /* flip_b0 */); }
 		if (*lut_str)
 			printf(" s0_D6LUT \"%s\"\n", lut_str);
 
 		lut64 = read_lut64(&maj_bits[27*130], frame_off+32);
-		lut_str = lut2bool(lut64, 64);
+		{  int logic_base[6] = {1,1,0,1,1,0};
+		   lut_str = lut2bool(lut64, 64, &logic_base, 0 /* flip_b0 */); }
 		if (*lut_str)
 			printf(" s1_A6LUT \"%s\"\n", lut_str);
 
 		lut64 = read_lut64(&maj_bits[29*130], frame_off+32);
-		lut_str = lut2bool(lut64, 64);
+		{  int logic_base[6] = {1,1,0,1,1,0};
+		   lut_str = lut2bool(lut64, 64, &logic_base, 0 /* flip_b0 */); }
 		if (*lut_str)
 			printf(" s1_B6LUT \"%s\"\n", lut_str);
 
 		lut64 = read_lut64(&maj_bits[27*130], frame_off);
-		lut_str = lut2bool(lut64, 64);
+		{  int logic_base[6] = {0,1,0,0,0,1};
+		   lut_str = lut2bool(lut64, 64, &logic_base, 0 /* flip_b0 */); }
 		if (*lut_str)
 			printf(" s1_C6LUT \"%s\"\n", lut_str);
 
 		lut64 = read_lut64(&maj_bits[29*130], frame_off);
-		lut_str = lut2bool(lut64, 64);
+		{  int logic_base[6] = {0,1,0,0,0,1};
+		   lut_str = lut2bool(lut64, 64, &logic_base, 0 /* flip_b0 */); }
 		if (*lut_str)
 			printf(" s1_D6LUT \"%s\"\n", lut_str);
 
@@ -609,8 +617,8 @@ void printf_bits(uint8_t* bits, int bits_len, int idcode)
 				for (minor = 20; minor < 31; minor++)
 					printf_clock(&bits[off+minor*130],
 						row, major, minor);
-				// extra bits at bottom of row0 and top of row2
-				if (row == 2)
+				// extra bits at bottom of row0 and top of row3
+				if (row == 3)
 					printf_singlebits(&bits[off], 20, 11,
 						0, 128, row, major);
 				else if (!row)
diff --git a/helper.c b/helper.c
index f678ef1..d538eda 100644
--- a/helper.c
+++ b/helper.c
@@ -246,6 +246,7 @@ int parse_boolexpr(const char* expr, uint64_t* lut)
 		}
 		if (((i&8) != 0) ^ ((i&4) != 0))
 			vars[2] = 1;
+		// todo: flip_b0 and different base values missing
 		result = bool_eval(expr, strlen(expr), vars);
 		if (result == -1) return -1;
 		if (result) *lut |= 1LL<<i;
@@ -261,6 +262,7 @@ void printf_lut6(const char* cfg)
 
 	first_major = 0;
 	second_major = 0;
+	// todo: this is missing the different base_values, flip_b0 etc.
 	parse_boolexpr(cfg, &lut);
 
 	for (i = 0; i < 16; i++) {
@@ -283,7 +285,8 @@ typedef struct _minterm_entry
 } minterm_entry;
 
 // bits is tested only for 32 and 64
-const char* lut2bool(const uint64_t lut, int bits)
+const char* lut2bool(const uint64_t lut, int bits,
+	int (*logic_base)[6], int flip_b0)
 {
 	// round 0 needs 64 entries
 	// round 1 (size2): 192
@@ -303,12 +306,12 @@ const char* lut2bool(const uint64_t lut, int bits)
 
 	for (i = 0; i < bits; i++) {
 		if (lut & (1LL<<i)) {
-			mt[0][mt_size[0]].a[0] = lut_base_vars[0];
-			mt[0][mt_size[0]].a[1] = lut_base_vars[1];
-			mt[0][mt_size[0]].a[2] = lut_base_vars[2];
-			mt[0][mt_size[0]].a[3] = lut_base_vars[3];
-			mt[0][mt_size[0]].a[4] = lut_base_vars[4];
-			mt[0][mt_size[0]].a[5] = lut_base_vars[5];
+			mt[0][mt_size[0]].a[0] = (*logic_base)[0];
+			mt[0][mt_size[0]].a[1] = (*logic_base)[1];
+			mt[0][mt_size[0]].a[2] = (*logic_base)[2];
+			mt[0][mt_size[0]].a[3] = (*logic_base)[3];
+			mt[0][mt_size[0]].a[4] = (*logic_base)[4];
+			mt[0][mt_size[0]].a[5] = (*logic_base)[5];
 			for (j = 0; j < 6; j++) {
 				if (j != 2 && (i&(1<<j)))
 					mt[0][mt_size[0]].a[j]
@@ -316,6 +319,9 @@ const char* lut2bool(const uint64_t lut, int bits)
 			}
 			if (((i&8) != 0) ^ ((i&4) != 0))
 				mt[0][mt_size[0]].a[2] = 1;
+			if (flip_b0
+			   && (mt[0][mt_size[0]].a[2] ^ mt[0][mt_size[0]].a[3]))
+			  mt[0][mt_size[0]].a[0] = !mt[0][mt_size[0]].a[0];
 			mt_size[0]++;
 		}
 	}
@@ -411,250 +417,14 @@ const char* lut2bool(const uint64_t lut, int bits)
 	return str;
 }
 
-static const char* iob_xc6slx4_sitenames[896*2/8] =
-{
-	[0x0000/8] "P70",
-		   "P69",
-		   "P67",
-		   "P66",
-		   "P65",
-		   "P64",
-		   "P62",
-		   "P61",
-		   "P60",
-		   "P59",
-		   "P58",
-		   "P57",
-		   0,
-		   0,
-		   0,
-		   0,
-	[0x0080/8] 0,
-		   0,
-		   "P56",
-		   "P55",
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   "P51",
-		   "P50",
-		   0,
-		   0,
-		   0,
-		   0,
-	[0x0100/8] 0,
-		   0,
-		   0,
-		   0,
-		   "UNB131",
-		   "UNB132",
-		   "P48",
-		   "P47",
-		   "P46",
-		   "P45",
-		   "P44",
-		   "P43",
-		   0,
-		   0,
-		   "P41",
-		   "P40",
-	[0x0180/8] "P39",
-		   "P38",
-		   "P35",
-		   "P34",
-		   "P33",
-		   "P32",
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-	[0x0200/8] "P30",
-		   "P29",
-		   "P27",
-		   "P26",
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   "P24",
-		   "P23",
-		   "P22",
-		   "P21",
-		   0,
-		   0,
-	[0x0280/8] 0,
-		   0,
-		   0,
-		   0,
-		   "P17",
-		   "P16",
-		   "P15",
-		   "P14",
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-	[0x0300/8] "P12",
-		   "P11",
-		   "P10",
-		   "P9",
-		   "P8",
-		   "P7",
-		   "P6",
-		   "P5",
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   "P2",
-		   "P1",
-	[0x0380/8] "P144",
-		   "P143",
-		   "P142",
-		   "P141",
-		   "P140",
-		   "P139",
-		   "P138",
-		   "P137",
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-	[0x0400/8] 0,
-		   0,
-		   0,
-		   0,
-		   "P134",
-		   "P133",
-		   "P132",
-		   "P131",
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   "P127",
-		   "P126",
-	[0x0480/8] "P124",
-		   "P123",
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   "P121",
-		   "P120",
-		   "P119",
-		   "P118",
-		   "P117",
-		   "P116",
-		   "P115",
-		   "P114",
-	[0x0500/8] "P112",
-		   "P111",
-		   "P105",
-		   "P104",
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   "P102",
-		   "P101",
-		   "P99",
-		   "P98",
-		   "P97",
-	[0x0580/8] 0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   "P95",
-		   "P94",
-		   "P93",
-		   "P92",
-		   0,
-		   0,
-	[0x0600/8] 0,
-		   0,
-		   0,
-		   "P88",
-		   "P87",
-		   0,
-		   "P85",
-		   "P84",
-		   0,
-		   0,
-		   "P83",
-		   "P82",
-		   "P81",
-		   "P80",
-		   "P79",
-		   "P78",
-	[0x0680/8] 0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   0,
-		   "P75",
-		   "P74"
-};
-
 int printf_iob(uint8_t* d, int len, int inpos, int num_entries)
 {
 	int i, j, num_printed;
 
 	num_printed = 0;
-	if (num_entries != sizeof(iob_xc6slx4_sitenames)/sizeof(iob_xc6slx4_sitenames[0]))
-		printf("#W Expected %li IOB entries but got %i.\n",
-			sizeof(iob_xc6slx4_sitenames)/sizeof(iob_xc6slx4_sitenames[0]),
-			num_entries);
 	for (i = 0; i < num_entries; i++) {
-		if (*(uint32_t*)&d[inpos+i*8]
-		    || *(uint32_t*)&d[inpos+i*8+4]) {
-			if (i < sizeof(iob_xc6slx4_sitenames)/sizeof(iob_xc6slx4_sitenames[0])
-			    && iob_xc6slx4_sitenames[i]) {
-				printf("iob %s", iob_xc6slx4_sitenames[i]);
-			} else
-				printf("iob %i", i);
+		if (*(uint32_t*)&d[inpos+i*8] || *(uint32_t*)&d[inpos+i*8+4]) {
+			printf("iob i%i", i);
 			for (j = 0; j < 8; j++)
 				printf(" %02X", d[inpos+i*8+j]);
 			printf("\n");
diff --git a/helper.h b/helper.h
index 46a08ae..6921eee 100644
--- a/helper.h
+++ b/helper.h
@@ -48,7 +48,8 @@ int printf_header(uint8_t* d, int len, int inpos, int* outdelta);
 
 void printf_lut6(const char* cfg);
 // bits is tested only for 32 and 64
-const char* lut2bool(const uint64_t lut, int bits);
+const char* lut2bool(const uint64_t lut, int bits,
+	int (*logic_base)[6], int flip_b0);
 
 int printf_iob(uint8_t* d, int len, int inpos, int num_entries);
 void printf_ramb16_data(uint8_t* bits, int inpos);
diff --git a/not-needed.h b/not-needed.h
new file mode 100644
index 0000000..a4cc5c3
--- /dev/null
+++ b/not-needed.h
@@ -0,0 +1,233 @@
+//
+// Author: Wolfgang Spraul
+//
+// This is free and unencumbered software released into the public domain.
+// For details see the UNLICENSE file at the root of the source tree.
+//
+
+static const char* iob_xc6slx4_sitenames[896*2/8] =
+{
+	[0x0000/8] "P70",
+		   "P69",
+		   "P67",
+		   "P66",
+		   "P65",
+		   "P64",
+		   "P62",
+		   "P61",
+		   "P60",
+		   "P59",
+		   "P58",
+		   "P57",
+		   0,
+		   0,
+		   0,
+		   0,
+	[0x0080/8] 0,
+		   0,
+		   "P56",
+		   "P55",
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   "P51",
+		   "P50",
+		   0,
+		   0,
+		   0,
+		   0,
+	[0x0100/8] 0,
+		   0,
+		   0,
+		   0,
+		   "UNB131",
+		   "UNB132",
+		   "P48",
+		   "P47",
+		   "P46",
+		   "P45",
+		   "P44",
+		   "P43",
+		   0,
+		   0,
+		   "P41",
+		   "P40",
+	[0x0180/8] "P39",
+		   "P38",
+		   "P35",
+		   "P34",
+		   "P33",
+		   "P32",
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+	[0x0200/8] "P30",
+		   "P29",
+		   "P27",
+		   "P26",
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   "P24",
+		   "P23",
+		   "P22",
+		   "P21",
+		   0,
+		   0,
+	[0x0280/8] 0,
+		   0,
+		   0,
+		   0,
+		   "P17",
+		   "P16",
+		   "P15",
+		   "P14",
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+	[0x0300/8] "P12",
+		   "P11",
+		   "P10",
+		   "P9",
+		   "P8",
+		   "P7",
+		   "P6",
+		   "P5",
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   "P2",
+		   "P1",
+	[0x0380/8] "P144",
+		   "P143",
+		   "P142",
+		   "P141",
+		   "P140",
+		   "P139",
+		   "P138",
+		   "P137",
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+	[0x0400/8] 0,
+		   0,
+		   0,
+		   0,
+		   "P134",
+		   "P133",
+		   "P132",
+		   "P131",
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   "P127",
+		   "P126",
+	[0x0480/8] "P124",
+		   "P123",
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   "P121",
+		   "P120",
+		   "P119",
+		   "P118",
+		   "P117",
+		   "P116",
+		   "P115",
+		   "P114",
+	[0x0500/8] "P112",
+		   "P111",
+		   "P105",
+		   "P104",
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   "P102",
+		   "P101",
+		   "P99",
+		   "P98",
+		   "P97",
+	[0x0580/8] 0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   "P95",
+		   "P94",
+		   "P93",
+		   "P92",
+		   0,
+		   0,
+	[0x0600/8] 0,
+		   0,
+		   0,
+		   "P88",
+		   "P87",
+		   0,
+		   "P85",
+		   "P84",
+		   0,
+		   0,
+		   "P83",
+		   "P82",
+		   "P81",
+		   "P80",
+		   "P79",
+		   "P78",
+	[0x0680/8] 0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   0,
+		   "P75",
+		   "P74"
+};