diff --git a/.gitignore b/.gitignore
index c5b22dc..16aeaf3 100644
--- a/.gitignore
+++ b/.gitignore
@@ -22,7 +22,8 @@ floorplan.o
 control.o
 autotest
 autotest.o
-bits.o
+bit_regs.o
+bit_frames.o
 fp2bit
 fp2bit.o
 bit2fp
diff --git a/Makefile b/Makefile
index f7d9b91..4eeff4f 100644
--- a/Makefile
+++ b/Makefile
@@ -28,17 +28,19 @@ new_fp: new_fp.o $(MODEL_OBJ) floorplan.o helper.o control.o
 
 new_fp.o: new_fp.c floorplan.h model.h helper.h control.h
 
-fp2bit: fp2bit.o $(MODEL_OBJ) floorplan.o control.o bits.o helper.o
+fp2bit: fp2bit.o $(MODEL_OBJ) floorplan.o control.o bit_regs.o bit_frames.o helper.o
 
-fp2bit.o: fp2bit.c model.h floorplan.h bits.h helper.h
+fp2bit.o: fp2bit.c model.h floorplan.h bit.h helper.h
 
-bit2fp: bit2fp.o $(MODEL_OBJ) floorplan.o control.o bits.o helper.o
+bit2fp: bit2fp.o $(MODEL_OBJ) floorplan.o control.o bit_regs.o bit_frames.o helper.o
 
-bit2fp.o: bit2fp.c model.h floorplan.h bits.h helper.h
+bit2fp.o: bit2fp.c model.h floorplan.h bit.h helper.h
 
 floorplan.o: floorplan.c floorplan.h model.h control.h
 
-bits.o: bits.c bits.h model.h
+bit_regs.o: bit_regs.c bit.h model.h
+
+bit_frames.o: bit_frames.c bit.h model.h
 
 control.o: control.c control.h model.h
 
@@ -127,6 +129,7 @@ clean:
 		autotest autotest.o control.o floorplan.o \
 		fp2bit fp2bit.o \
 		bit2fp bit2fp.o \
+		bit_regs.o bit_frames.o \
 		pair2net pair2net.o \
 		xc6slx9_empty.fp xc6slx9.svg \
 		xc6slx9_empty.tiles xc6slx9_empty.devs xc6slx9_empty.conns \
diff --git a/bits.h b/bit.h
similarity index 97%
rename from bits.h
rename to bit.h
index 12f72bf..04b49bd 100644
--- a/bits.h
+++ b/bit.h
@@ -108,7 +108,6 @@ struct fpga_config
 };
 
 int read_bitfile(struct fpga_config* cfg, FILE* f);
-int extract_model(struct fpga_model* model, uint8_t* bits, int bits_len);
 
 #define DUMP_HEADER_STR		0x0001
 #define DUMP_REGS		0x0002
@@ -118,3 +117,6 @@ int dump_config(struct fpga_config* cfg, int flags);
 void free_config(struct fpga_config* cfg);
 
 int write_bitfile(FILE* f, struct fpga_model* model);
+
+int extract_model(struct fpga_model* model, uint8_t* bits, int bits_len);
+int write_model(uint8_t* bits, int bits_len, struct fpga_model* model);
diff --git a/bit2fp.c b/bit2fp.c
index 48d62a7..30d557e 100644
--- a/bit2fp.c
+++ b/bit2fp.c
@@ -7,7 +7,7 @@
 
 #include "model.h"
 #include "floorplan.h"
-#include "bits.h"
+#include "bit.h"
 
 int main(int argc, char** argv)
 {
diff --git a/bit_frames.c b/bit_frames.c
new file mode 100644
index 0000000..b667eeb
--- /dev/null
+++ b/bit_frames.c
@@ -0,0 +1,19 @@
+//
+// 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.
+//
+
+#include "model.h"
+#include "bit.h"
+
+int extract_model(struct fpga_model* model, uint8_t* bits, int bits_len)
+{
+	return 0;
+}
+
+int write_model(uint8_t* bits, int bits_len, struct fpga_model* model)
+{
+	return 0;
+}
diff --git a/bits.c b/bit_regs.c
similarity index 99%
rename from bits.c
rename to bit_regs.c
index 810abd6..e2a23a2 100644
--- a/bits.c
+++ b/bit_regs.c
@@ -6,7 +6,7 @@
 //
 
 #include "model.h"
-#include "bits.h"
+#include "bit.h"
 
 static int parse_header(struct fpga_config* config, uint8_t* d,
 	int len, int inpos, int* outdelta);
@@ -97,11 +97,6 @@ fail:
 	return rc;
 }
 
-int extract_model(struct fpga_model* model, uint8_t* bits, int bits_len)
-{
-	return 0;
-}
-
 static void dump_header(struct fpga_config* cfg)
 {
 	int i;
@@ -1681,11 +1676,6 @@ fail:
 	return rc;
 }
 
-static int write_model(uint8_t* bits, int bits_len, struct fpga_model* model)
-{
-	return 0;
-}
-
 static int write_bits(FILE* f, struct fpga_model* model)
 {
 	uint8_t* bits;
diff --git a/fp2bit.c b/fp2bit.c
index 5db8c9c..9e32a0d 100644
--- a/fp2bit.c
+++ b/fp2bit.c
@@ -7,7 +7,7 @@
 
 #include "model.h"
 #include "floorplan.h"
-#include "bits.h"
+#include "bit.h"
 
 int main(int argc, char** argv)
 {