diff --git a/include/jtag/data_register.h b/include/jtag/data_register.h
index 5d9cb4d1..61fcf2c2 100644
--- a/include/jtag/data_register.h
+++ b/include/jtag/data_register.h
@@ -31,8 +31,8 @@ typedef struct data_register data_register;
 
 struct data_register {
 	char *name;		/* (public) register name */
-	tap_register *value;	/* (public) register value */
-	tap_register *oldval;	/* (private) temporary (old) register value */
+	tap_register *in;	/* (public) register value clocked in */
+	tap_register *out;	/* (public) register value clocked out */
 	data_register *next;
 };
 
diff --git a/include/jtag/part.h b/include/jtag/part.h
index daac564e..8eb6092c 100644
--- a/include/jtag/part.h
+++ b/include/jtag/part.h
@@ -49,6 +49,8 @@ void part_free( part *p );
 part *read_part( FILE *f, tap_register *idr );
 instruction *part_find_instruction( part *p, const char *iname );
 data_register *part_find_data_register( part *p, const char *drname );
+void part_shift_instruction( part *p, int exit );
+void part_shift_data_register( part *p, int exit );
 void part_set_signal( part *p, const char *pname, int out, int val );
 int part_get_signal( part *p, const char *pname );
 
diff --git a/jtag/src/part/data_register.c b/jtag/src/part/data_register.c
index f7eb6a89..6824a3cb 100644
--- a/jtag/src/part/data_register.c
+++ b/jtag/src/part/data_register.c
@@ -45,11 +45,11 @@ data_register_alloc( const char *name, int len )
 		return NULL;
 	}
 
-	dr->value = register_alloc( len );
-	dr->oldval = register_alloc( len );
-	if (!dr->value || !dr->oldval) {
-		free( dr->value );
-		free( dr->oldval );
+	dr->in = register_alloc( len );
+	dr->out = register_alloc( len );
+	if (!dr->in || !dr->out) {
+		free( dr->in );
+		free( dr->out );
 		free( dr->name );
 		free( dr );
 		return NULL;
@@ -67,7 +67,7 @@ data_register_free( data_register *dr )
 		return;
 
 	free( dr->name );
-	register_free( dr->value );
-	register_free( dr->oldval );
+	register_free( dr->in );
+	register_free( dr->out );
 	free( dr );
 }
diff --git a/jtag/src/part/parse.c b/jtag/src/part/parse.c
index 542d9d95..8459c2be 100644
--- a/jtag/src/part/parse.c
+++ b/jtag/src/part/parse.c
@@ -136,7 +136,7 @@ read_part( FILE *f, tap_register *idr )
 
 			/* Device Identification Register */
 			if (strcmp( dr->name, "DIR" ) == 0)
-				register_init( dr->value, register_get_string( idr ) );
+				register_init( dr->out, register_get_string( idr ) );
 
 			continue;
 		}
@@ -220,7 +220,7 @@ read_part( FILE *f, tap_register *idr )
 			/* get bit number */
 			t = get_token( NULL );
 			bit = strtol( t, &t, 10 );
-			if ((t && *t) || (bit < 0) || (bit >= bsr->value->len)) {
+			if ((t && *t) || (bit < 0) || (bit >= bsr->in->len)) {
 				printf( "(%d) invalid boundary bit number\n", line );
 				continue;
 			}
@@ -260,7 +260,7 @@ read_part( FILE *f, tap_register *idr )
 				continue;
 			}
 			safe = (*t == '1') ? 1 : 0;
-			bsr->value->data[bit] = safe;
+			bsr->in->data[bit] = safe;
 
 			/* get bit name */
 			t = get_token( NULL );
diff --git a/jtag/src/part/part.c b/jtag/src/part/part.c
index f25465a4..c41a0f00 100644
--- a/jtag/src/part/part.c
+++ b/jtag/src/part/part.c
@@ -121,6 +121,24 @@ part_find_data_register( part *p, const char *drname )
 	return dr;
 }
 
+void
+part_shift_instruction( part *p, int exit )
+{
+	if (!p || !p->active_instruction)
+		return;
+
+	tap_shift_register( p->active_instruction->value, NULL, exit );
+}
+
+void
+part_shift_data_register( part *p, int exit )
+{
+	if (!p || !p->active_instruction || !p->active_instruction->data_register)
+		return;
+	
+	tap_shift_register( p->active_instruction->data_register->in, p->active_instruction->data_register->out, exit );
+}
+
 void
 part_set_signal( part *p, const char *pname, int out, int val )
 {
@@ -153,18 +171,18 @@ part_set_signal( part *p, const char *pname, int out, int val )
 			printf( "signal %s cannot be set as output\n", pname );
 			return;
 		}
-		bsr->value->data[s->output->bit] = val & 1;
+		bsr->in->data[s->output->bit] = val & 1;
 
 		control = p->bsbits[s->output->bit]->control;
 		if (control >= 0)
-			bsr->value->data[control] = p->bsbits[s->output->bit]->control_value ^ 1;
+			bsr->in->data[control] = p->bsbits[s->output->bit]->control_value ^ 1;
 	} else {
 		if (!s->input) {
 			printf( "signal %s cannot be set as input\n", pname );
 			return;
 		}
 		if (s->output)
-			bsr->value->data[s->output->control] = p->bsbits[s->output->control]->control_value;
+			bsr->in->data[s->output->control] = p->bsbits[s->output->control]->control_value;
 	}
 }
 
@@ -198,7 +216,7 @@ part_get_signal( part *p, const char *pname )
 		return -1;
 	}
 
-	return bsr->value->data[s->input->bit];
+	return bsr->out->data[s->input->bit];
 }
 
 /* parts */