diff --git a/Makefile b/Makefile
index 7a168e3..73fab62 100644
--- a/Makefile
+++ b/Makefile
@@ -21,13 +21,17 @@ all: autotest bit2txt draw_svg_tiles new_fp fp2bit hstrrep sort_seq merge_seq
 
 autotest: autotest.o $(MODEL_OBJ) floorplan.o control.o helper.o model.h
 
+autotest.c: model.h floorplan.h control.h
+
 new_fp: new_fp.o $(MODEL_OBJ) floorplan.o helper.o
 
 new_fp.o: new_fp.c floorplan.h model.h helper.h
 
-fp2bit: fp2bit.c $(MODEL_OBJ) bits.o helper.o
+fp2bit: fp2bit.o $(MODEL_OBJ) floorplan.o control.o bits.o helper.o
 
-floorplan.o: floorplan.c floorplan.h model.h
+fp2bit.o: fp2bit.c model.h floorplan.h bits.h helper.h
+
+floorplan.o: floorplan.c floorplan.h model.h control.h
 
 bits.o: bits.c bits.h model.h
 
diff --git a/README b/README
index 2b0d594..52bd2e8 100644
--- a/README
+++ b/README
@@ -4,7 +4,7 @@ Design Principles
 - plain C, no C++
 - simple Makefiles
 - text-based file formats
-- no documentation - read the sources
+- no documentation - please read the sources
 - automatic test suite
 
 Libraries
diff --git a/autotest.c b/autotest.c
index af6ffe0..ce975e3 100644
--- a/autotest.c
+++ b/autotest.c
@@ -85,7 +85,13 @@ int main(int argc, char** argv)
 	dev->iob.slew = SLEW_SLOW;
 	dev->iob.suspend = SUSP_3STATE;
 
-	// todo: configure logic
+	// configure logic
+	dev = fpga_dev(&model, /*y*/ 68, /*x*/ 13, DEV_LOGIC, /*LOGIC_X*/ 1);
+	EXIT(!dev);
+	dev->instantiated = 1;
+	dev->logic.D_used = 1;
+	rc = fpga_set_lut(&model, dev, D6_LUT, "A3", ZTERM);
+	EXIT(rc);
 
 	mkdir(AUTOTEST_TMP_DIR, S_IRWXU|S_IRWXG|S_IROTH|S_IXOTH);
 	dest_f = fopen(AUTOTEST_TMP_DIR "/test_0001.fp", "w");
diff --git a/bits.c b/bits.c
index 42d8d6b..89a18c5 100644
--- a/bits.c
+++ b/bits.c
@@ -7,3 +7,8 @@
 
 #include "model.h"
 #include "bits.h"
+
+int write_bits(FILE* f, struct fpga_model* model)
+{
+	return 0;
+}
diff --git a/bits.h b/bits.h
index 0d6562e..658210e 100644
--- a/bits.h
+++ b/bits.h
@@ -4,3 +4,5 @@
 // This is free and unencumbered software released into the public domain.
 // For details see the UNLICENSE file at the root of the source tree.
 //
+
+int write_bits(FILE* f, struct fpga_model* model);
diff --git a/control.c b/control.c
index ea5595f..1c5b7d9 100644
--- a/control.c
+++ b/control.c
@@ -156,6 +156,50 @@ int fpga_find_iob(struct fpga_model* model, const char* sitename,
 	return -1;
 }
 
+const char* fpga_iob_sitename(struct fpga_model* model, int y, int x,
+	int idx)
+{
+	int i;
+
+	if (y == TOP_OUTER_ROW) {
+		for (i = 0; i < sizeof(xc6slx9_iob_top)/sizeof(xc6slx9_iob_top[0]); i++) {
+			if (xc6slx9_iob_right[i].xy == x) {
+				if (idx < 0 || idx > 3) return 0;
+				return xc6slx9_iob_top[i].name[idx];
+			}
+		}
+		return 0;
+	}
+	if (y == model->y_height-BOT_OUTER_ROW) {
+		for (i = 0; i < sizeof(xc6slx9_iob_bottom)/sizeof(xc6slx9_iob_bottom[0]); i++) {
+			if (xc6slx9_iob_bottom[i].xy == x) {
+				if (idx < 0 || idx > 3) return 0;
+				return xc6slx9_iob_bottom[i].name[idx];
+			}
+		}
+		return 0;
+	}
+	if (x == LEFT_OUTER_COL) {
+		for (i = 0; i < sizeof(xc6slx9_iob_left)/sizeof(xc6slx9_iob_left[0]); i++) {
+			if (xc6slx9_iob_left[i].xy == y) {
+				if (idx < 0 || idx > 1) return 0;
+				return xc6slx9_iob_left[i].name[idx];
+			}
+		}
+		return 0;
+	}
+	if (x == model->x_width-RIGHT_OUTER_O) {
+		for (i = 0; i < sizeof(xc6slx9_iob_right)/sizeof(xc6slx9_iob_right[0]); i++) {
+			if (xc6slx9_iob_right[i].xy == y) {
+				if (idx < 0 || idx > 1) return 0;
+				return xc6slx9_iob_right[i].name[idx];
+			}
+		}
+		return 0;
+	}
+	return 0;
+}
+
 struct fpga_device* fpga_dev(struct fpga_model* model,
 	int y, int x, enum fpgadev_type type, int idx)
 {
@@ -173,3 +217,32 @@ struct fpga_device* fpga_dev(struct fpga_model* model,
 	}
 	return 0;
 }
+
+#define MAX_LUT_LEN	512
+
+int fpga_set_lut(struct fpga_model* model, struct fpga_device* dev,
+	int which_lut, const char* lut_str, int lut_len)
+{
+	char** ptr;
+
+	if (dev->type != DEV_LOGIC)
+		return -1;
+	switch (which_lut) {
+		case A6_LUT: ptr = &dev->logic.A6_lut; break;
+		case B6_LUT: ptr = &dev->logic.B6_lut; break;
+		case C6_LUT: ptr = &dev->logic.C6_lut; break;
+		case D6_LUT: ptr = &dev->logic.D6_lut; break;
+		default: return -1;
+	}
+	if (!(*ptr)) {
+		*ptr = malloc(MAX_LUT_LEN);
+		if (!(*ptr)) {
+			OUT_OF_MEM();
+			return -1;
+		}
+	}
+	if (lut_len == ZTERM) lut_len = strlen(lut_str);
+	memcpy(*ptr, lut_str, lut_len);
+	(*ptr)[lut_len] = 0;
+	return 0;
+}
diff --git a/control.h b/control.h
index 8cfd597..fa3f22c 100644
--- a/control.h
+++ b/control.h
@@ -8,5 +8,13 @@
 int fpga_find_iob(struct fpga_model* model, const char* sitename,
 	int* y, int* x, int* idx);
 
+const char* fpga_iob_sitename(struct fpga_model* model, int y, int x,
+	int idx);
+
 struct fpga_device* fpga_dev(struct fpga_model* model,
 	int y, int x, enum fpgadev_type type, int idx);
+
+enum { A6_LUT, B6_LUT, C6_LUT, D6_LUT };
+// lut_len can be -1 (ZTERM)
+int fpga_set_lut(struct fpga_model* model, struct fpga_device* dev,
+	int which_lut, const char* lut_str, int lut_len);
diff --git a/floorplan.c b/floorplan.c
index fd4b82a..e2d7404 100644
--- a/floorplan.c
+++ b/floorplan.c
@@ -8,6 +8,7 @@
 #include <stdarg.h>
 
 #include "model.h"
+#include "control.h"
 #include "floorplan.h"
 
 void printf_version(FILE* f)
@@ -146,7 +147,7 @@ static int printf_IOB(FILE* f, struct fpga_model* model,
 			case 0: break; default: EXIT(1);
 		}
 		if (tile->devs[i].iob.O_used)
-			printf_wrap(f, line, plen, "o_used");
+			printf_wrap(f, line, plen, "O_used");
 		switch (tile->devs[i].iob.suspend) {
 			case SUSP_LAST_VAL:
 				printf_wrap(f, line, plen, "suspend DRIVE_LAST_VALUE");
@@ -204,6 +205,109 @@ static int printf_IOB(FILE* f, struct fpga_model* model,
 	return 0;
 }
 
+static int read_IOB_attr(struct fpga_model* model, struct fpga_device* dev,
+	const char* w1, int w1_len, const char* w2, int w2_len)
+{
+	// First the one-word attributes.
+	if (!str_cmp(w1, w1_len, "O_used", ZTERM)) {
+		dev->iob.O_used = 1;
+		goto inst_1;
+	}
+	// The remaining attributes all require 2 words.
+	if (w2_len < 1) return 0;
+	if (!str_cmp(w1, w1_len, "type", ZTERM))
+		return 2; // no reason for instantiation
+	if (!str_cmp(w1, w1_len, "istd", ZTERM)) {
+		memcpy(dev->iob.istandard, w2, w2_len);
+		dev->iob.istandard[w2_len] = 0;
+		goto inst_2;
+	}
+	if (!str_cmp(w1, w1_len, "ostd", ZTERM)) {
+		memcpy(dev->iob.ostandard, w2, w2_len);
+		dev->iob.ostandard[w2_len] = 0;
+		goto inst_2;
+	}
+	if (!str_cmp(w1, w1_len, "bypass_mux", ZTERM)) {
+		if (!str_cmp(w2, w2_len, "I", ZTERM))
+			dev->iob.bypass_mux = BYPASS_MUX_I;
+		else if (!str_cmp(w2, w2_len, "O", ZTERM))
+			dev->iob.bypass_mux = BYPASS_MUX_O;
+		else if (!str_cmp(w2, w2_len, "T", ZTERM))
+			dev->iob.bypass_mux = BYPASS_MUX_T;
+		else return 0;
+		goto inst_2;
+	}
+	if (!str_cmp(w1, w1_len, "imux", ZTERM)) {
+		if (!str_cmp(w2, w2_len, "I_B", ZTERM))
+			dev->iob.I_mux = IMUX_I_B;
+		else if (!str_cmp(w2, w2_len, "I", ZTERM))
+			dev->iob.I_mux = IMUX_I;
+		else return 0;
+		goto inst_2;
+	}
+	if (!str_cmp(w1, w1_len, "strength", ZTERM)) {
+		dev->iob.drive_strength = to_i(w2, w2_len);
+		goto inst_2;
+	}
+	if (!str_cmp(w1, w1_len, "slew", ZTERM)) {
+		if (!str_cmp(w2, w2_len, "SLOW", ZTERM))
+			dev->iob.slew = SLEW_SLOW;
+		else if (!str_cmp(w2, w2_len, "FAST", ZTERM))
+			dev->iob.slew = SLEW_FAST;
+		else if (!str_cmp(w2, w2_len, "QUIETIO", ZTERM))
+			dev->iob.slew = SLEW_QUIETIO;
+		else return 0;
+		goto inst_2;
+	}
+	if (!str_cmp(w1, w1_len, "suspend", 7)) {
+		if (!str_cmp(w2, w2_len, "DRIVE_LAST_VALUE", ZTERM))
+			dev->iob.suspend = SUSP_LAST_VAL;
+		else if (!str_cmp(w2, w2_len, "3STATE", ZTERM))
+			dev->iob.suspend = SUSP_3STATE;
+		else if (!str_cmp(w2, w2_len, "3STATE_PULLUP", ZTERM))
+			dev->iob.suspend = SUSP_3STATE_PULLUP;
+		else if (!str_cmp(w2, w2_len, "3STATE_PULLDOWN", ZTERM))
+			dev->iob.suspend = SUSP_3STATE_PULLDOWN;
+		else if (!str_cmp(w2, w2_len, "3STATE_KEEPER", ZTERM))
+			dev->iob.suspend = SUSP_3STATE_KEEPER;
+		else if (!str_cmp(w2, w2_len, "3STATE_OCT_ON", ZTERM))
+			dev->iob.suspend = SUSP_3STATE_OCT_ON;
+		else return 0;
+		goto inst_2;
+	}
+	if (!str_cmp(w1, w1_len, "in_term", ZTERM)) {
+		if (!str_cmp(w2, w2_len, "NONE", ZTERM))
+			dev->iob.in_term = ITERM_NONE;
+		else if (!str_cmp(w2, w2_len, "UNTUNED_SPLIT_25", ZTERM))
+			dev->iob.in_term = ITERM_UNTUNED_25;
+		else if (!str_cmp(w2, w2_len, "UNTUNED_SPLIT_50", ZTERM))
+			dev->iob.in_term = ITERM_UNTUNED_50;
+		else if (!str_cmp(w2, w2_len, "UNTUNED_SPLIT_75", ZTERM))
+			dev->iob.in_term = ITERM_UNTUNED_75;
+		else return 0;
+		goto inst_2;
+	}
+	if (!str_cmp(w1, w1_len, "out_term", ZTERM)) {
+		if (!str_cmp(w2, w2_len, "NONE", ZTERM))
+			dev->iob.out_term = OTERM_NONE;
+		else if (!str_cmp(w2, w2_len, "UNTUNED_25", ZTERM))
+			dev->iob.out_term = OTERM_UNTUNED_25;
+		else if (!str_cmp(w2, w2_len, "UNTUNED_50", ZTERM))
+			dev->iob.out_term = OTERM_UNTUNED_50;
+		else if (!str_cmp(w2, w2_len, "UNTUNED_75", ZTERM))
+			dev->iob.out_term = OTERM_UNTUNED_75;
+		else return 0;
+		goto inst_2;
+	}
+	return 0;
+inst_1:
+	dev->instantiated = 1;
+	return 1;
+inst_2:
+	dev->instantiated = 2;
+	return 2;
+}
+
 static int printf_LOGIC(FILE* f, struct fpga_model* model,
 	int y, int x, int config_only)
 {
@@ -237,12 +341,85 @@ static int printf_LOGIC(FILE* f, struct fpga_model* model,
 				break;
 			default: EXIT(1);
 		}
+		if (tile->devs[i].logic.A_used)
+			printf_wrap(f, line, plen, "A_used");
+		if (tile->devs[i].logic.B_used)
+			printf_wrap(f, line, plen, "B_used");
+		if (tile->devs[i].logic.C_used)
+			printf_wrap(f, line, plen, "C_used");
+		if (tile->devs[i].logic.D_used)
+			printf_wrap(f, line, plen, "D_used");
+		if (tile->devs[i].logic.A6_lut && tile->devs[i].logic.A6_lut[0])
+			printf_wrap(f, line, plen, "A6_lut %s",
+				tile->devs[i].logic.A6_lut);
+		if (tile->devs[i].logic.B6_lut && tile->devs[i].logic.B6_lut[0])
+			printf_wrap(f, line, plen, "B6_lut %s",
+				tile->devs[i].logic.B6_lut);
+		if (tile->devs[i].logic.C6_lut && tile->devs[i].logic.C6_lut[0])
+			printf_wrap(f, line, plen, "C6_lut %s",
+				tile->devs[i].logic.C6_lut);
+		if (tile->devs[i].logic.D6_lut && tile->devs[i].logic.D6_lut[0])
+			printf_wrap(f, line, plen, "D6_lut %s",
+				tile->devs[i].logic.D6_lut);
 		strcat(line, "\n");
 		fprintf(f, line);
 	}
 	return 0;
 }
 
+static int read_LOGIC_attr(struct fpga_model* model, struct fpga_device* dev,
+	const char* w1, int w1_len, const char* w2, int w2_len)
+{
+	// First the one-word attributes.
+	if (!str_cmp(w1, w1_len, "A_used", ZTERM)) {
+		dev->logic.A_used = 1;
+		goto inst_1;
+	}
+	if (!str_cmp(w1, w1_len, "B_used", ZTERM)) {
+		dev->logic.B_used = 1;
+		goto inst_1;
+	}
+	if (!str_cmp(w1, w1_len, "C_used", ZTERM)) {
+		dev->logic.C_used = 1;
+		goto inst_1;
+	}
+	if (!str_cmp(w1, w1_len, "D_used", ZTERM)) {
+		dev->logic.D_used = 1;
+		goto inst_1;
+	}
+	// The remaining attributes all require 2 words.
+	if (w2_len < 1) return 0;
+	if (!str_cmp(w1, w1_len, "type", ZTERM))
+		return 2; // no reason for instantiation
+	if (!str_cmp(w1, w1_len, "A6_lut", ZTERM)) {
+		if (fpga_set_lut(model, dev, A6_LUT, w2, w2_len))
+			return 0;
+		goto inst_2;
+	}
+	if (!str_cmp(w1, w1_len, "B6_lut", ZTERM)) {
+		if (fpga_set_lut(model, dev, B6_LUT, w2, w2_len))
+			return 0;
+		goto inst_2;
+	}
+	if (!str_cmp(w1, w1_len, "C6_lut", ZTERM)) {
+		if (fpga_set_lut(model, dev, C6_LUT, w2, w2_len))
+			return 0;
+		goto inst_2;
+	}
+	if (!str_cmp(w1, w1_len, "D6_lut", ZTERM)) {
+		if (fpga_set_lut(model, dev, D6_LUT, w2, w2_len))
+			return 0;
+		goto inst_2;
+	}
+	return 0;
+inst_1:
+	dev->instantiated = 1;
+	return 1;
+inst_2:
+	dev->instantiated = 2;
+	return 2;
+}
+
 int printf_devices(FILE* f, struct fpga_model* model, int config_only)
 {
 	int x, y, i, rc;
@@ -332,6 +509,7 @@ int printf_devices(FILE* f, struct fpga_model* model, int config_only)
 						break;
 					case DEV_IOB:
 					case DEV_LOGIC:
+					case DEV_NONE:
 						// to suppress compiler warning
 						break;
 				}
@@ -483,3 +661,99 @@ int printf_switches(FILE* f, struct fpga_model* model, int enabled_only)
 	}
 	return 0;
 }
+
+static enum fpgadev_type to_type(const char* s, int len)
+{
+	if (!str_cmp(s, len, "IOB", 3)) return DEV_IOB;
+	if (!str_cmp(s, len, "LOGIC", 5)) return DEV_LOGIC;
+	return DEV_NONE;
+}
+
+int read_floorplan(struct fpga_model* model, FILE* f)
+{
+	char line[1024];
+	int beg, end;
+
+	while (fgets(line, sizeof(line), f)) {
+		next_word(line, 0, &beg, &end);
+		if (end == beg) continue;
+
+		if (!str_cmp(&line[beg], end-beg, "dev", 3)) {
+			int y_beg, y_end, x_beg, x_end;
+			int y_coord, x_coord;
+			int type_beg, type_end, idx_beg, idx_end;
+			enum fpgadev_type dev_type;
+			int dev_idx, words_consumed;
+			struct fpga_device* dev_ptr;
+			int next_beg, next_end, second_beg, second_end;
+
+			next_word(line, end, &y_beg, &y_end);
+			next_word(line, y_end, &x_beg, &x_end);
+			if (y_end < y_beg+2 || x_end < x_beg+2
+			    || line[y_beg] != 'y' || line[x_beg] != 'x'
+			    || !all_digits(&line[y_beg+1], y_end-y_beg-1)
+			    || !all_digits(&line[x_beg+1], x_end-x_beg-1)) {
+				fprintf(stderr, "error %i: %s", __LINE__, line);
+				continue;
+			}
+			y_coord = to_i(&line[y_beg+1], y_end-y_beg-1);
+			x_coord = to_i(&line[x_beg+1], x_end-x_beg-1);
+
+			next_word(line, x_end, &type_beg, &type_end);
+			next_word(line, type_end, &idx_beg, &idx_end);
+
+			if (type_end == type_beg || idx_end == idx_beg
+			    || !all_digits(&line[idx_beg], idx_end-idx_beg)) {
+				fprintf(stderr, "error %i: %s", __LINE__, line);
+				continue;
+			}
+			dev_type = to_type(&line[type_beg], type_end-type_beg);
+			dev_idx = to_i(&line[idx_beg], idx_end-idx_beg);
+			dev_ptr = fpga_dev(model, y_coord, x_coord, dev_type, dev_idx);
+			if (!dev_ptr) {
+				fprintf(stderr, "error %i: %s", __LINE__, line);
+				continue;
+			}
+
+			next_end = idx_end;
+			while (next_word(line, next_end, &next_beg, &next_end),
+				next_end > next_beg) {
+				next_word(line, next_end, &second_beg, &second_end);
+				switch (dev_type) {
+					case DEV_IOB:
+						words_consumed = read_IOB_attr(
+							model, dev_ptr,
+							&line[next_beg],
+							next_end-next_beg,
+							&line[second_beg],
+							second_end-second_beg);
+						break;
+					case DEV_LOGIC:
+						words_consumed = read_LOGIC_attr(
+							model, dev_ptr,
+							&line[next_beg],
+							next_end-next_beg,
+							&line[second_beg],
+							second_end-second_beg);
+						break;
+					default:
+						fprintf(stderr, "error %i: %s",
+							__LINE__, line);
+						goto next_line;
+				}
+				if (!words_consumed)
+					fprintf(stderr,
+						"error %i w1 %.*s w2 %.*s: %s",
+						__LINE__, next_end-next_beg,
+						&line[next_beg],
+						second_end-second_beg,
+						&line[second_beg],
+						line);
+				else if (words_consumed == 2)
+					next_end = second_end;
+			}
+next_line: ;
+		}
+	}
+	return 0;
+}
diff --git a/floorplan.h b/floorplan.h
index 439be5b..e88500e 100644
--- a/floorplan.h
+++ b/floorplan.h
@@ -24,6 +24,8 @@
 // - lines should typically not exceed 80 characters
 //
 
+int read_floorplan(struct fpga_model* model, FILE* f);
+
 void printf_version(FILE* f);
 int printf_tiles(FILE* f, struct fpga_model* model);
 int printf_devices(FILE* f, struct fpga_model* model, int config_only);
diff --git a/fp2bit.c b/fp2bit.c
index 0002ebe..3caea7d 100644
--- a/fp2bit.c
+++ b/fp2bit.c
@@ -6,17 +6,45 @@
 //
 
 #include "model.h"
+#include "floorplan.h"
 #include "bits.h"
 
 int main(int argc, char** argv)
 {
 	struct fpga_model model;
-	int rc;
+	FILE* fp, *fbits;
+	int rc = -1;
+
+	if (argc != 3) {
+		fprintf(stderr,
+			"\n"
+			"%s - floorplan to bitstream\n"
+			"Usage: %s <floorplan_file|- for stdin> <bits_file>\n"
+			"\n", argv[0], argv[0]);
+		goto fail;
+	}
+
+	if (!strcmp(argv[1], "-"))
+		fp = stdin;
+	else {
+		fp = fopen(argv[1], "r");
+		if (!fp) {
+			fprintf(stderr, "Error opening %s.\n", argv[1]);
+			goto fail;
+		}
+	}
+	fbits = fopen(argv[2], "w");
+	if (!fbits) {
+		fprintf(stderr, "Error opening %s.\n", argv[2]);
+		goto fail;
+	}
 
 	if ((rc = fpga_build_model(&model, XC6SLX9_ROWS, XC6SLX9_COLUMNS,
 			XC6SLX9_LEFT_WIRING, XC6SLX9_RIGHT_WIRING)))
 		goto fail;
 
+	if ((rc = read_floorplan(&model, fp))) goto fail;
+	if ((rc = write_bits(fbits, &model))) goto fail;
 	return EXIT_SUCCESS;
 fail:
 	return rc;
diff --git a/helper.c b/helper.c
index c5741bc..aa30579 100644
--- a/helper.c
+++ b/helper.c
@@ -702,6 +702,47 @@ void next_word(const char*s, int start, int* beg, int* end)
 	*end = i;
 }
 
+int str_cmp(const char* a, int a_len, const char* b, int b_len)
+{
+	int i = 0;
+
+	if (a_len == -1) {
+		a_len = 0;
+		while (a[a_len]) a_len++;
+	}
+	if (b_len == -1) {
+		b_len = 0;
+		while (b[b_len]) b_len++;
+	}
+	while (1) {
+		if (i >= a_len) {
+			if (i >= b_len)
+				return 0;
+			return -1;
+		}
+		if (i >= b_len) {
+			if (i >= a_len)
+				return 0;
+			return 1;
+		}
+		if (a[i] != b[i])
+			return a[i] - b[i];
+		i++;
+	}
+}
+
+int all_digits(const char* a, int len)
+{
+	int i;
+
+	if (!len) return 0;
+	for (i = 0; i < len; i++) {
+		if (a[i] < '0' || a[i] > '9')
+			return 0;
+	}
+	return 1;
+}
+
 int to_i(const char* s, int len)
 {
 	int num, base;
diff --git a/helper.h b/helper.h
index f5abb01..8d7fbaa 100644
--- a/helper.h
+++ b/helper.h
@@ -16,6 +16,8 @@
 #define PROGRAM_REVISION "2012-06-27"
 #define MACRO_STR(arg)	#arg
 
+#define OUT_OF_MEM()	{ fprintf(stderr, \
+	"Out of memory in %s:%i\n", __FILE__, __LINE__); }
 #define EXIT(expr)	if (expr) { fprintf(stderr, \
 	"Internal error in %s:%i\n", __FILE__, __LINE__); exit(1); }
 
@@ -77,7 +79,13 @@ uint64_t read_lut64(uint8_t* two_minors, int off_in_frame);
 int get_vm_mb(void);
 int get_random(void);
 int compare_with_number(const char* a, const char* b);
+// If no next word is found, *end == *beg
 void next_word(const char* s, int start, int* beg, int* end);
+// if a_len or b_len are -1, the length is until 0-termination
+#define ZTERM -1
+int str_cmp(const char* a, int a_len, const char* b, int b_len);
+// all_digits() returns 0 if len == 0
+int all_digits(const char* a, int len);
 int to_i(const char* s, int len);
 
 uint32_t hash_djb2(const unsigned char* str);
diff --git a/model.h b/model.h
index faa0414..9049197 100644
--- a/model.h
+++ b/model.h
@@ -168,7 +168,7 @@ enum fpga_tile_type
 #define CENTER_LOGIC_O		2
 #define CENTER_ROUTING_O	3
 
-#define YX_TILE(model, y, x) (&(model)->tiles[(y)*model->x_width+(x)])
+#define YX_TILE(model, y, x) (&(model)->tiles[(y)*(model)->x_width+(x)])
 
 // tile flags
 
@@ -271,6 +271,8 @@ const char* logicin_s(int wire, int routing_io);
 
 enum fpgadev_type
 {
+	DEV_NONE = 0,
+
 	DEV_LOGIC,
 	DEV_TIEOFF,
 	DEV_MACC,
diff --git a/model_devices.c b/model_devices.c
index 05a6832..0ce5bdb 100644
--- a/model_devices.c
+++ b/model_devices.c
@@ -325,13 +325,14 @@ int init_devices(struct fpga_model* model)
 		if (!is_atx(X_LOGIC_COL, model, x))
 			continue;
 		for (y = TOP_IO_TILES; y < model->y_height - BOT_IO_TILES; y++) {
+			// M and L are at index 0, X is at index 1.
 			if (YX_TILE(model, y, x)->flags & TF_LOGIC_XM_DEV) {
-				if ((rc = add_dev(model, y, x, DEV_LOGIC, LOGIC_X))) goto fail;
 				if ((rc = add_dev(model, y, x, DEV_LOGIC, LOGIC_M))) goto fail;
+				if ((rc = add_dev(model, y, x, DEV_LOGIC, LOGIC_X))) goto fail;
 			}
 			if (YX_TILE(model, y, x)->flags & TF_LOGIC_XL_DEV) {
-				if ((rc = add_dev(model, y, x, DEV_LOGIC, LOGIC_X))) goto fail;
 				if ((rc = add_dev(model, y, x, DEV_LOGIC, LOGIC_L))) goto fail;
+				if ((rc = add_dev(model, y, x, DEV_LOGIC, LOGIC_X))) goto fail;
 			}
 		}
 	}
diff --git a/sort_seq.c b/sort_seq.c
index 12be30a..49514fa 100644
--- a/sort_seq.c
+++ b/sort_seq.c
@@ -106,27 +106,6 @@ static void find_number(const char* s, int s_len, int* num_start, int* num_end)
 	}
 }
 
-static int str_cmp(const char* a, int a_len, const char* b, int b_len)
-{
-	int i = 0;
-
-	while (1) {
-		if (i >= a_len) {
-			if (i >= b_len)
-				return 0;
-			return -1;
-		}
-		if (i >= b_len) {
-			if (i >= a_len)
-				return 0;
-			return 1;
-		}
-		if (a[i] != b[i])
-			return a[i] - b[i];
-		i++;
-	}
-}
-
 static int is_known_suffix(const char* str, int str_len)
 {
 	int i;