diff --git a/README b/README
index 8514117..b3ef2dd 100644
--- a/README
+++ b/README
@@ -63,7 +63,6 @@ Design Principles
 TODO (as of February, 2013)
 
 short-term (1 month):
-* finish lut_encoding test
 * finish dist_mem test
 * support block memory
 * example: counter (including clock, jtag)
diff --git a/libs/control.c b/libs/control.c
index 78a46cf..0dc6879 100644
--- a/libs/control.c
+++ b/libs/control.c
@@ -838,8 +838,7 @@ int fdev_set_required_pins(struct fpga_model* model, int y, int x, int type,
 	int type_idx)
 {
 	struct fpga_device* dev;
-	int req_inpins[6];
-	int i, j, k, rc;
+	int req_inpins, i, j, rc;
 
 	RC_CHECK(model);
 	dev = fdev_p(model, y, x, type, type_idx);
@@ -897,32 +896,18 @@ int fdev_set_required_pins(struct fpga_model* model, int y, int x, int type,
 				add_req_inpin(dev, LI_AX+i);
 			}
 
-			for (j = 0; j < 6; j++)
-				req_inpins[j] = 0;
+			req_inpins = 0;
 			if (dev->u.logic.a2d[i].flags & LUT5VAL_SET) {
 				// A6 must be high/vcc if lut5 is used
-				req_inpins[5] = 1;
-				for (j = 0; j < 32; j++) {
-					if (!(dev->u.logic.a2d[i].lut5_val & (1ULL << j)))
-						continue;
-					for (k = 0; k < 5; k++) {
-						if (j & (1<<k))
-							req_inpins[k] = 1;
-					}
-				}
+				req_inpins |= 1<<5;
+				req_inpins |= bool_req_pins(dev->u.logic.a2d[i].lut5_val, 32);
 			}
 			if (dev->u.logic.a2d[i].flags & LUT6VAL_SET) {
-				for (j = 0; j < 64; j++) {
-					if (!(dev->u.logic.a2d[i].lut6_val & (1ULL << j)))
-						continue;
-					for (k = 0; k < 6; k++) {
-						if (j & (1<<k))
-							req_inpins[k] = 1;
-					}
-				}
+				req_inpins |= bool_req_pins(dev->u.logic.a2d[i].lut6_val,
+					(dev->u.logic.a2d[i].flags & LUT5VAL_SET) ? 32 : 64);
 			}
 			for (j = 0; j < 6; j++) {
-				if (req_inpins[j])
+				if (req_inpins & (1<<j))
 					add_req_inpin(dev, LI_A1+i*6+j);
 			}
 			if ((dev->u.logic.a2d[i].ff_mux == MUX_XOR
diff --git a/libs/helper.c b/libs/helper.c
index 1602d8c..265fea4 100644
--- a/libs/helper.c
+++ b/libs/helper.c
@@ -122,6 +122,8 @@ static int bool_nextlen(const char *expr, int len)
 		if (expr[i] < '1' || expr[i] > '6') return -1;
 		return i+1;
 	}
+	if (expr[i] == '0' || expr[i] == '1')
+		return i+1;
 	return -1;
 }
 
@@ -236,7 +238,11 @@ int bool_str2bits(const char *str, int str_len, uint64_t *u64, int num_bits)
 		for (j = 0; j < sizeof(vars)/sizeof(*vars); j++)
 			vars[j] = (i & (1<<j)) != 0;
 		bool_res = bool_eval(str, str_len, vars);
-		if (bool_res == -1) FAIL(EINVAL);
+		if (bool_res == -1) {
+			fprintf(stderr, "#E %s:%i cannot evaluate '%.*s'\n",
+				__FILE__, __LINE__, str_len, str);
+			FAIL(EINVAL);
+		}
 		if (bool_res) *u64 |= 1ULL<<i;
 	}
 	return 0;
@@ -265,17 +271,13 @@ const char* bool_bits2str(uint64_t u64, int num_bits)
 	int str_end, first_op, bit_width;
 	static char str[2048];
 
-	if (!u64) return "0";
 	if (num_bits == 64) {
+		if (!u64) return "0";
 		if (u64 == 0xFFFFFFFFFFFFFFFFULL) return "1";
 		bit_width = 6;
 	} else if (num_bits == 32) {
-		if (u64 & 0xFFFFFFFF00000000ULL) {
-			// upper 32 bits should be 0
-			HERE();
-			return "0";
-		}
-		if (u64 == 0x00000000FFFFFFFFULL) return "1";
+		if (!ULL_LOW32(u64)) return "0";
+		if (ULL_LOW32(u64) == 0xFFFFFFFF) return "1";
 		bit_width = 5;
 	} else {
 		HERE();
@@ -370,6 +372,37 @@ const char* bool_bits2str(uint64_t u64, int num_bits)
 	return str;
 }
 
+int bool_req_pins(uint64_t u64, int num_bits)
+{
+	static const uint64_t pin_mask[6] = {
+		0xAAAAAAAAAAAAAAAA, /*A1*/
+		0xCCCCCCCCCCCCCCCC, /*A2*/
+		0xF0F0F0F0F0F0F0F0, /*A3*/
+		0xFF00FF00FF00FF00, /*A4*/
+		0xFFFF0000FFFF0000, /*A5*/
+		0xFFFFFFFF00000000  /*A6*/ };
+	uint64_t bit_mask;
+	int req_pins, num_pins, i;
+
+	if (num_bits == 32) {
+		num_pins = 5;
+		bit_mask = 0x00000000FFFFFFFF;
+	} else {
+		if (num_bits != 64) HERE();
+		num_pins = 6;
+		bit_mask = 0xFFFFFFFFFFFFFFFF;
+	}
+	// Special cases of all bits 0 and all bits 1 will
+	// correctly lead to req_pins == 0 because all bits
+	// are the same.
+	req_pins = 0;
+	for (i = 0; i < num_pins; i++) {
+		if ((u64 & pin_mask[i] & bit_mask) >> (1<<i) != (u64 & ~pin_mask[i] & bit_mask))
+			req_pins |= 1<<i;
+	}
+	return req_pins;
+}
+
 void printf_type2(uint8_t *d, int len, int inpos, int num_entries)
 {
 	uint64_t u64;
diff --git a/libs/helper.h b/libs/helper.h
index 137cef8..aa8a2b9 100644
--- a/libs/helper.h
+++ b/libs/helper.h
@@ -72,6 +72,7 @@ int bool_str2u32(const char *str, uint32_t *u32);
 int bool_str2lut_pair(const char *str6, const char *str5, uint64_t *lut6_val, uint32_t *lut5_val);
 int bool_str2bits(const char* str, int str_len, uint64_t* u64, int num_bits);
 const char* bool_bits2str(uint64_t u64, int num_bits);
+int bool_req_pins(uint64_t u64, int num_bits);
 
 void printf_type2(uint8_t* d, int len, int inpos, int num_entries);
 void printf_ramb16_data(uint8_t* bits, int inpos);
diff --git a/libs/model.h b/libs/model.h
index d035acb..c2cc18e 100644
--- a/libs/model.h
+++ b/libs/model.h
@@ -416,7 +416,6 @@ enum {
 	  "COUT" }
 
 enum { LUT_A = 0, LUT_B, LUT_C, LUT_D }; // offset into a2d[]
-enum { LUTMODE_LUT = 1, LUTMODE_ROM, LUTMODE_RAM };
 #define OUT_USED	0x0001
 #define LUT5VAL_SET	0x0002
 #define LUT6VAL_SET	0x0004