diff --git a/Makefile b/Makefile
index 0991f47..cad1926 100644
--- a/Makefile
+++ b/Makefile
@@ -36,10 +36,12 @@ include Makefile.common
 libs/%.so: FAKE
 	@make -C libs $(notdir $@)
 
-test: test_logic_cfg test_routing_sw
+test: test_logic_cfg test_iob_cfg test_routing_sw
 
 test_logic_cfg: autotest.out/autotest_logic_cfg.diff_to_gold
 
+test_iob_cfg: autotest.out/autotest_iob_cfg.diff_to_gold
+
 test_routing_sw: autotest.out/autotest_routing_sw.diff_to_gold
 
 autotest_%.diff_to_gold: autotest_%.log
diff --git a/autotest.gold/autotest_iob_cfg.log b/autotest.gold/autotest_iob_cfg.log
new file mode 100644
index 0000000..2e4c4d6
--- /dev/null
+++ b/autotest.gold/autotest_iob_cfg.log
@@ -0,0 +1,310 @@
+
+O fpgatools automatic test suite. Be welcome and be our guest. namo namaha.
+
+O Test: iob_cfg
+O Diff: ./autotest_diff.sh
+O Skip: 0
+O Dry run: 0
+
+O Time measured in seconds from 0.
+O #NODIFF timestamp 0
+O Memory usage reported in megabytes.
+O #NODIFF memusage 25
+O Building memory model...
+O Done
+O #NODIFF timestamp 4
+O #NODIFF memusage 85
+
+O begin dump autotest.tmp/autotest_iob_cfg_000001.diff
+fp:
++dev y72 x12 IOB 1 istd LVCMOS33
++dev y72 x12 IOB 1 bypass_mux I
++dev y72 x12 IOB 1 imux I
+bit:
++dev y72 x12 IOB 1 istd LVCMOS33
++dev y72 x12 IOB 1 bypass_mux I
++dev y72 x12 IOB 1 imux I
+O end dump autotest.tmp/autotest_iob_cfg_000001.diff
+
+O begin dump autotest.tmp/autotest_iob_cfg_000002.diff
+fp:
++dev y72 x12 IOB 1 istd LVCMOS33
++dev y72 x12 IOB 1 bypass_mux I
++dev y72 x12 IOB 1 imux I_B
+bit:
++dev y72 x12 IOB 1 istd LVCMOS33
++dev y72 x12 IOB 1 bypass_mux I
++dev y72 x12 IOB 1 imux I_B
+O end dump autotest.tmp/autotest_iob_cfg_000002.diff
+
+O begin dump autotest.tmp/autotest_iob_cfg_000003.diff
+fp:
++dev y72 x12 IOB 0 istd LVCMOS33
++dev y72 x12 IOB 0 bypass_mux I
++dev y72 x12 IOB 0 imux I
+bit:
++dev y72 x12 IOB 0 istd LVCMOS33
++dev y72 x12 IOB 0 bypass_mux I
++dev y72 x12 IOB 0 imux I
+O end dump autotest.tmp/autotest_iob_cfg_000003.diff
+
+O begin dump autotest.tmp/autotest_iob_cfg_000004.diff
+fp:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 8
++dev y72 x12 IOB 2 slew SLOW
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend 3STATE
+bit:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 8
++dev y72 x12 IOB 2 slew SLOW
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend 3STATE
+O end dump autotest.tmp/autotest_iob_cfg_000004.diff
+
+O begin dump autotest.tmp/autotest_iob_cfg_000005.diff
+fp:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 8
++dev y72 x12 IOB 2 slew SLOW
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend 3STATE_OCT_ON
+bit:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 8
++dev y72 x12 IOB 2 slew SLOW
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend 3STATE_OCT_ON
+O end dump autotest.tmp/autotest_iob_cfg_000005.diff
+
+O begin dump autotest.tmp/autotest_iob_cfg_000006.diff
+fp:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 8
++dev y72 x12 IOB 2 slew SLOW
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend 3STATE_KEEPER
+bit:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 8
++dev y72 x12 IOB 2 slew SLOW
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend 3STATE_KEEPER
+O end dump autotest.tmp/autotest_iob_cfg_000006.diff
+
+O begin dump autotest.tmp/autotest_iob_cfg_000007.diff
+fp:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 8
++dev y72 x12 IOB 2 slew SLOW
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend 3STATE_PULLUP
+bit:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 8
++dev y72 x12 IOB 2 slew SLOW
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend 3STATE_PULLUP
+O end dump autotest.tmp/autotest_iob_cfg_000007.diff
+
+O begin dump autotest.tmp/autotest_iob_cfg_000008.diff
+fp:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 8
++dev y72 x12 IOB 2 slew SLOW
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend 3STATE_PULLDOWN
+bit:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 8
++dev y72 x12 IOB 2 slew SLOW
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend 3STATE_PULLDOWN
+O end dump autotest.tmp/autotest_iob_cfg_000008.diff
+
+O begin dump autotest.tmp/autotest_iob_cfg_000009.diff
+fp:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 8
++dev y72 x12 IOB 2 slew SLOW
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend DRIVE_LAST_VALUE
+bit:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 8
++dev y72 x12 IOB 2 slew SLOW
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend DRIVE_LAST_VALUE
+O end dump autotest.tmp/autotest_iob_cfg_000009.diff
+
+O begin dump autotest.tmp/autotest_iob_cfg_000010.diff
+fp:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 2
++dev y72 x12 IOB 2 slew SLOW
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend 3STATE
+bit:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 2
++dev y72 x12 IOB 2 slew SLOW
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend 3STATE
+O end dump autotest.tmp/autotest_iob_cfg_000010.diff
+
+O begin dump autotest.tmp/autotest_iob_cfg_000011.diff
+fp:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 4
++dev y72 x12 IOB 2 slew SLOW
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend 3STATE
+bit:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 4
++dev y72 x12 IOB 2 slew SLOW
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend 3STATE
+O end dump autotest.tmp/autotest_iob_cfg_000011.diff
+
+O begin dump autotest.tmp/autotest_iob_cfg_000012.diff
+fp:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 6
++dev y72 x12 IOB 2 slew SLOW
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend 3STATE
+bit:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 6
++dev y72 x12 IOB 2 slew SLOW
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend 3STATE
+O end dump autotest.tmp/autotest_iob_cfg_000012.diff
+
+O begin dump autotest.tmp/autotest_iob_cfg_000013.diff
+fp:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 8
++dev y72 x12 IOB 2 slew SLOW
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend 3STATE
+bit:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 8
++dev y72 x12 IOB 2 slew SLOW
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend 3STATE
+O end dump autotest.tmp/autotest_iob_cfg_000013.diff
+
+O begin dump autotest.tmp/autotest_iob_cfg_000014.diff
+fp:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 12
++dev y72 x12 IOB 2 slew SLOW
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend 3STATE
+bit:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 12
++dev y72 x12 IOB 2 slew SLOW
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend 3STATE
+O end dump autotest.tmp/autotest_iob_cfg_000014.diff
+
+O begin dump autotest.tmp/autotest_iob_cfg_000015.diff
+fp:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 16
++dev y72 x12 IOB 2 slew SLOW
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend 3STATE
+bit:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 16
++dev y72 x12 IOB 2 slew SLOW
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend 3STATE
+O end dump autotest.tmp/autotest_iob_cfg_000015.diff
+
+O begin dump autotest.tmp/autotest_iob_cfg_000016.diff
+fp:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 24
++dev y72 x12 IOB 2 slew SLOW
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend 3STATE
+bit:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 24
++dev y72 x12 IOB 2 slew SLOW
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend 3STATE
+O end dump autotest.tmp/autotest_iob_cfg_000016.diff
+
+O begin dump autotest.tmp/autotest_iob_cfg_000017.diff
+fp:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 8
++dev y72 x12 IOB 2 slew SLOW
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend 3STATE
+bit:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 8
++dev y72 x12 IOB 2 slew SLOW
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend 3STATE
+O end dump autotest.tmp/autotest_iob_cfg_000017.diff
+
+O begin dump autotest.tmp/autotest_iob_cfg_000018.diff
+fp:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 8
++dev y72 x12 IOB 2 slew FAST
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend 3STATE
+bit:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 8
++dev y72 x12 IOB 2 slew FAST
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend 3STATE
+O end dump autotest.tmp/autotest_iob_cfg_000018.diff
+
+O begin dump autotest.tmp/autotest_iob_cfg_000019.diff
+fp:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 8
++dev y72 x12 IOB 2 slew QUIETIO
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend 3STATE
+bit:
++dev y72 x12 IOB 2 ostd LVCMOS33
++dev y72 x12 IOB 2 strength 8
++dev y72 x12 IOB 2 slew QUIETIO
++dev y72 x12 IOB 2 O_used
++dev y72 x12 IOB 2 suspend 3STATE
+O end dump autotest.tmp/autotest_iob_cfg_000019.diff
+
+O begin dump autotest.tmp/autotest_iob_cfg_000020.diff
+fp:
++dev y72 x12 IOB 3 ostd LVCMOS33
++dev y72 x12 IOB 3 strength 8
++dev y72 x12 IOB 3 slew SLOW
++dev y72 x12 IOB 3 O_used
++dev y72 x12 IOB 3 suspend 3STATE
++net 1 in y72 x12 IOB 3 pin O
+bit:
++dev y72 x12 IOB 3 ostd LVCMOS33
++dev y72 x12 IOB 3 strength 8
++dev y72 x12 IOB 3 slew SLOW
++dev y72 x12 IOB 3 O_used
++dev y72 x12 IOB 3 suspend 3STATE
+O end dump autotest.tmp/autotest_iob_cfg_000020.diff
+
+O Test completed.
+O #NODIFF timestamp 1055
+O #NODIFF memusage 85
+
diff --git a/libs/bit_frames.c b/libs/bit_frames.c
index 9952ebc..a18e455 100644
--- a/libs/bit_frames.c
+++ b/libs/bit_frames.c
@@ -161,8 +161,8 @@ static int write_iobs(struct fpga_bits* bits, struct fpga_model* model)
 			}
 			switch (dev->u.iob.slew) {
 				case SLEW_SLOW: u64 |= XC6_IOB_SLEW_SLOW; break;
-				case SLEW_QUIETIO: u64 |= XC6_IOB_SLEW_QUIETIO; break;
 				case SLEW_FAST: u64 |= XC6_IOB_SLEW_FAST; break;
+				case SLEW_QUIETIO: u64 |= XC6_IOB_SLEW_QUIETIO; break;
 				default: HERE();
 			}
 			switch (dev->u.iob.suspend) {
@@ -250,11 +250,6 @@ static int extract_iobs(struct fpga_model* model, struct fpga_bits* bits)
 			case XC6_IOB_OUTPUT_LVCMOS33_DRIVE_12:
 			case XC6_IOB_OUTPUT_LVCMOS33_DRIVE_16:
 			case XC6_IOB_OUTPUT_LVCMOS33_DRIVE_24:
-				u64 &= ~XC6_IOB_MASK_IO;
-				u64 &= ~XC6_IOB_MASK_O_PINW;
-
-				strcpy(cfg.ostandard, IO_LVCMOS33);
-				cfg.O_used = 1;
 				switch (u64 & XC6_IOB_MASK_IO) {
 					case XC6_IOB_OUTPUT_LVCMOS33_DRIVE_2:
 						cfg.drive_strength = 2; break;
@@ -270,21 +265,25 @@ static int extract_iobs(struct fpga_model* model, struct fpga_bits* bits)
 						cfg.drive_strength = 16; break;
 					case XC6_IOB_OUTPUT_LVCMOS33_DRIVE_24:
 						cfg.drive_strength = 24; break;
-					default: HERE();
+					default: HERE(); break;
 				}
+				u64 &= ~XC6_IOB_MASK_IO;
+				u64 &= ~XC6_IOB_MASK_O_PINW;
+				strcpy(cfg.ostandard, IO_LVCMOS33);
+				cfg.O_used = 1;
 				switch (u64 & XC6_IOB_MASK_SLEW) {
 					case XC6_IOB_SLEW_SLOW:
 						u64 &= ~XC6_IOB_MASK_SLEW;
 						cfg.slew = SLEW_SLOW;
 						break;
-					case XC6_IOB_SLEW_QUIETIO:
-						u64 &= ~XC6_IOB_MASK_SLEW;
-						cfg.slew = SLEW_QUIETIO;
-						break;
 					case XC6_IOB_SLEW_FAST:
 						u64 &= ~XC6_IOB_MASK_SLEW;
 						cfg.slew = SLEW_FAST;
 						break;
+					case XC6_IOB_SLEW_QUIETIO:
+						u64 &= ~XC6_IOB_MASK_SLEW;
+						cfg.slew = SLEW_QUIETIO;
+						break;
 					default: HERE();
 				}
 				switch (u64 & XC6_IOB_MASK_SUSPEND) {
@@ -318,6 +317,8 @@ static int extract_iobs(struct fpga_model* model, struct fpga_bits* bits)
 			default: HERE(); break;
 		}
 		if (!u64) {
+			frame_set_u64(&bits->d[IOB_DATA_START
+				+ i*IOB_ENTRY_LEN], 0);
 			dev->instantiated = 1;
 			dev->u.iob = cfg;
 		} else HERE();
diff --git a/libs/bit_regs.c b/libs/bit_regs.c
index ec99e1f..92b88c0 100644
--- a/libs/bit_regs.c
+++ b/libs/bit_regs.c
@@ -1005,7 +1005,8 @@ static int FAR_pos(int FAR_row, int FAR_major, int FAR_minor)
 	return result + FAR_minor*130;
 }
 
-static int read_bits(struct fpga_config* cfg, uint8_t* d, int len, int inpos, int* outdelta)
+static int read_bits(struct fpga_config* cfg, uint8_t* d, int len,
+	int inpos, int* outdelta)
 {
 	int src_off, packet_hdr_type, packet_hdr_opcode;
 	int packet_hdr_register, packet_hdr_wordcount;
diff --git a/libs/helper.c b/libs/helper.c
index c47c08e..245bcc4 100644
--- a/libs/helper.c
+++ b/libs/helper.c
@@ -540,8 +540,12 @@ uint64_t frame_get_u64(uint8_t* frame_d)
 void frame_set_u8(uint8_t* frame_d, uint8_t v)
 {
 	int i;
-	for (i = 0; i < 8; i++)
-		if (v & (1<<(7-i))) (*frame_d) |= 1<<i;
+	for (i = 0; i < 8; i++) {
+		if (v & (1<<(7-i)))
+			(*frame_d) |= 1<<i;
+		else
+			(*frame_d) &= ~(1<<i);
+	}
 }
 
 void frame_set_u16(uint8_t* frame_d, uint16_t v)
diff --git a/libs/parts.h b/libs/parts.h
index 9ecd02b..23159e0 100644
--- a/libs/parts.h
+++ b/libs/parts.h
@@ -49,20 +49,20 @@
 #define XC6_IOB_MASK_SUSPEND			0x000000000000001F
 
 #define XC6_IOB_INSTANTIATED			0x0000000000000080
-#define XC6_IOB_INPUT_LVCMOS33			0x00D0024000000000
-#define XC6_IOB_OUTPUT_LVCMOS33_DRIVE_2		0x00100B4000000000
-#define XC6_IOB_OUTPUT_LVCMOS33_DRIVE_4		0x007006C000000000
-#define XC6_IOB_OUTPUT_LVCMOS33_DRIVE_6		0x00300FC000000000
+#define XC6_IOB_INPUT_LVCMOS33			0x00D0002400000000
+#define XC6_IOB_OUTPUT_LVCMOS33_DRIVE_2		0x001000B400000000
+#define XC6_IOB_OUTPUT_LVCMOS33_DRIVE_4		0x0070006C00000000
+#define XC6_IOB_OUTPUT_LVCMOS33_DRIVE_6		0x003000FC00000000
 #define XC6_IOB_OUTPUT_LVCMOS33_DRIVE_8		0x0040000000000000
-#define XC6_IOB_OUTPUT_LVCMOS33_DRIVE_12	0x0060088000000000
-#define XC6_IOB_OUTPUT_LVCMOS33_DRIVE_16	0x00980C6000000000
-#define XC6_IOB_OUTPUT_LVCMOS33_DRIVE_24	0x0088072000000000
+#define XC6_IOB_OUTPUT_LVCMOS33_DRIVE_12	0x0060008800000000
+#define XC6_IOB_OUTPUT_LVCMOS33_DRIVE_16	0x009800C600000000
+#define XC6_IOB_OUTPUT_LVCMOS33_DRIVE_24	0x0088007200000000
 #define XC6_IOB_O_PINW				0x0000000000000100
 #define XC6_IOB_IMUX_I				0x000000000000E000
 #define XC6_IOB_IMUX_I_B			0x000000000000E400
 #define XC6_IOB_SLEW_SLOW			0x0000000000000000
-#define XC6_IOB_SLEW_QUIETIO			0x0000000000330000
-#define XC6_IOB_SLEW_FAST			0x0000000000660000
+#define XC6_IOB_SLEW_FAST			0x0000000000330000
+#define XC6_IOB_SLEW_QUIETIO			0x0000000000660000
 #define XC6_IOB_SUSP_3STATE			0x0000000000000000
 #define XC6_IOB_SUSP_3STATE_OCT_ON		0x0000000000000001
 #define XC6_IOB_SUSP_3STATE_KEEPER		0x0000000000000002