diff --git a/artiq/coredevice/rt2wb.py b/artiq/coredevice/rt2wb.py
index 5bc3e6f7a..318d8bf0e 100644
--- a/artiq/coredevice/rt2wb.py
+++ b/artiq/coredevice/rt2wb.py
@@ -2,12 +2,6 @@ from artiq.language.core import *
 from artiq.language.types import *
 
 
-@syscall
-def rt2wb_output(time_mu: TInt64, channel: TInt32, addr: TInt32, data: TInt32
-                 ) -> TNone:
-    raise NotImplementedError("syscall not simulated")
-
-
 @syscall
 def rt2wb_input(channel: TInt32) -> TInt32:
     raise NotImplementedError("syscall not simulated")
diff --git a/artiq/coredevice/rtio.py b/artiq/coredevice/rtio.py
new file mode 100644
index 000000000..194818507
--- /dev/null
+++ b/artiq/coredevice/rtio.py
@@ -0,0 +1,13 @@
+from artiq.language.core import syscall
+from artiq.language.types import TInt64, TInt32, TNone
+
+
+@syscall
+def rtio_output(time_mu: TInt64, channel: TInt32, addr: TInt32, data: TInt32
+                ) -> TNone:
+    raise NotImplementedError("syscall not simulated")
+
+
+@syscall
+def rtio_input_timestamp(timeout_mu: TInt64, channel: TInt32) -> TInt64:
+    raise NotImplementedError("syscall not simulated")
diff --git a/artiq/coredevice/spi.py b/artiq/coredevice/spi.py
index 5b0c6bb88..5998997e1 100644
--- a/artiq/coredevice/spi.py
+++ b/artiq/coredevice/spi.py
@@ -1,7 +1,8 @@
 from artiq.language.core import (kernel, seconds_to_mu, now_mu,
                                  delay_mu, int)
 from artiq.language.units import MHz
-from artiq.coredevice.rt2wb import rt2wb_output, rt2wb_input
+from artiq.coredevice.rtio import rtio_output as rt2wb_output
+from artiq.coredevice.rt2wb import rt2wb_input
 
 
 SPI_DATA_ADDR, SPI_XFER_ADDR, SPI_CONFIG_ADDR = range(3)
diff --git a/artiq/coredevice/ttl.py b/artiq/coredevice/ttl.py
index 91c8c5531..1b3a6eecd 100644
--- a/artiq/coredevice/ttl.py
+++ b/artiq/coredevice/ttl.py
@@ -1,26 +1,6 @@
 from artiq.language.core import *
 from artiq.language.types import *
-
-
-@syscall
-def ttl_set_o(time_mu: TInt64, channel: TInt32, enabled: TBool) -> TNone:
-    raise NotImplementedError("syscall not simulated")
-
-@syscall
-def ttl_set_oe(time_mu: TInt64, channel: TInt32, enabled: TBool) -> TNone:
-    raise NotImplementedError("syscall not simulated")
-
-@syscall
-def ttl_set_sensitivity(time_mu: TInt64, channel: TInt32, sensitivity: TInt32) -> TNone:
-    raise NotImplementedError("syscall not simulated")
-
-@syscall
-def ttl_get(channel: TInt32, time_limit_mu: TInt64) -> TInt64:
-    raise NotImplementedError("syscall not simulated")
-
-@syscall
-def ttl_clock_set(time_mu: TInt64, channel: TInt32, ftw: TInt32) -> TNone:
-    raise NotImplementedError("syscall not simulated")
+from artiq.coredevice.rtio import rtio_output, rtio_input_timestamp
 
 
 class TTLOut:
@@ -39,7 +19,7 @@ class TTLOut:
 
     @kernel
     def set_o(self, o):
-        ttl_set_o(now_mu(), self.channel, o)
+        rtio_output(now_mu(), self.channel, 0, 1 if o else 0)
         self.o_previous_timestamp = now_mu()
 
     @kernel
@@ -108,7 +88,7 @@ class TTLInOut:
 
     @kernel
     def set_oe(self, oe):
-        ttl_set_oe(now_mu(), self.channel, oe)
+        rtio_output(now_mu(), self.channel, 1, 1 if oe else 0)
 
     @kernel
     def output(self):
@@ -128,7 +108,7 @@ class TTLInOut:
 
     @kernel
     def set_o(self, o):
-        ttl_set_o(now_mu(), self.channel, o)
+        rtio_output(now_mu(), self.channel, 0, 1 if o else 0)
         self.o_previous_timestamp = now_mu()
 
     @kernel
@@ -170,7 +150,7 @@ class TTLInOut:
 
     @kernel
     def _set_sensitivity(self, value):
-        ttl_set_sensitivity(now_mu(), self.channel, value)
+        rtio_output(now_mu(), self.channel, 2, 1 if value else 0)
         self.i_previous_timestamp = now_mu()
 
     @kernel
@@ -226,7 +206,7 @@ class TTLInOut:
         """Poll the RTIO input during all the previously programmed gate
         openings, and returns the number of registered events."""
         count = 0
-        while ttl_get(self.channel, self.i_previous_timestamp) >= 0:
+        while rtio_input_timestamp(self.i_previous_timestamp, self.channel) >= 0:
             count += 1
         return count
 
@@ -237,7 +217,7 @@ class TTLInOut:
 
         If the gate is permanently closed, returns a negative value.
         """
-        return ttl_get(self.channel, self.i_previous_timestamp)
+        return rtio_input_timestamp(self.i_previous_timestamp, self.channel)
 
 
 class TTLClockGen:
@@ -288,7 +268,7 @@ class TTLClockGen:
         that are not powers of two cause jitter of one RTIO clock cycle at the
         output.
         """
-        ttl_clock_set(now_mu(), self.channel, frequency)
+        rtio_output(now_mu(), self.channel, 0, frequency)
         self.previous_timestamp = now_mu()
 
     @kernel
diff --git a/artiq/runtime/Makefile b/artiq/runtime/Makefile
index 7915f4d0e..4411790dc 100644
--- a/artiq/runtime/Makefile
+++ b/artiq/runtime/Makefile
@@ -7,7 +7,7 @@ OBJECTS := isr.o clock.o rtiocrg.o flash_storage.o mailbox.o \
 	session.o log.o analyzer.o moninj.o net_server.o bridge_ctl.o \
 	ksupport_data.o kloader.o test_mode.o main.o
 OBJECTS_KSUPPORT := ksupport.o artiq_personality.o mailbox.o \
-	bridge.o rtio.o ttl.o rt2wb.o dds.o
+	bridge.o rtio.o rt2wb.o dds.o
 
 CFLAGS += -I$(LIBALLOC_DIRECTORY) \
 	-I$(MISOC_DIRECTORY)/software/include/dyld \
diff --git a/artiq/runtime/bridge.c b/artiq/runtime/bridge.c
index 708e35473..02be42e4c 100644
--- a/artiq/runtime/bridge.c
+++ b/artiq/runtime/bridge.c
@@ -1,21 +1,25 @@
 #include "mailbox.h"
 #include "messages.h"
 #include "rtio.h"
-#include "ttl.h"
 #include "dds.h"
 #include "bridge.h"
 
 #define TIME_BUFFER (8000 << CONFIG_RTIO_FINE_TS_WIDTH)
 
-static void dds_write(int addr, int data)
+static void rtio_output_blind(int channel, int addr, int data)
 {
-    rtio_chan_sel_write(CONFIG_RTIO_DDS_CHANNEL);
+    rtio_chan_sel_write(channel);
     rtio_o_address_write(addr);
     rtio_o_data_write(data);
     rtio_o_timestamp_write(rtio_get_counter() + TIME_BUFFER);
     rtio_o_we_write(1);
 }
 
+static void dds_write(int addr, int data)
+{
+    rtio_output_blind(CONFIG_RTIO_DDS_CHANNEL, addr, data);
+}
+
 static int dds_read(int addr)
 {
     int r;
@@ -54,7 +58,7 @@ void bridge_main(void)
                 struct msg_brg_ttl_out *msg;
 
                 msg = (struct msg_brg_ttl_out *)umsg;
-                ttl_set_oe(rtio_get_counter() + TIME_BUFFER, msg->channel, msg->value);
+                rtio_output_blind(msg->channel, 0, msg->value);
                 mailbox_acknowledge();
                 break;
             }
@@ -62,7 +66,7 @@ void bridge_main(void)
                 struct msg_brg_ttl_out *msg;
 
                 msg = (struct msg_brg_ttl_out *)umsg;
-                ttl_set_o(rtio_get_counter() + TIME_BUFFER, msg->channel, msg->value);
+                rtio_output_blind(msg->channel, 1, msg->value);
                 mailbox_acknowledge();
                 break;
             }
diff --git a/artiq/runtime/dds.c b/artiq/runtime/dds.c
index f76da5724..3f8e728c1 100644
--- a/artiq/runtime/dds.c
+++ b/artiq/runtime/dds.c
@@ -2,7 +2,7 @@
 #include <stdio.h>
 
 #include "artiq_personality.h"
-#include "rt2wb.h"
+#include "rtio.h"
 #include "log.h"
 #include "dds.h"
 
@@ -26,7 +26,7 @@
 #endif
 
 #define DDS_WRITE(addr, data) do { \
-        rt2wb_output(now, CONFIG_RTIO_DDS_CHANNEL, addr, data); \
+        rtio_output(now, CONFIG_RTIO_DDS_CHANNEL, addr, data); \
         now += DURATION_WRITE; \
     } while(0)
 
diff --git a/artiq/runtime/ksupport.c b/artiq/runtime/ksupport.c
index e15352bb5..add01a13a 100644
--- a/artiq/runtime/ksupport.c
+++ b/artiq/runtime/ksupport.c
@@ -13,7 +13,6 @@
 #include "messages.h"
 #include "bridge.h"
 #include "artiq_personality.h"
-#include "ttl.h"
 #include "dds.h"
 #include "rtio.h"
 #include "rt2wb.h"
@@ -110,19 +109,14 @@ static const struct symbol runtime_exports[] = {
     /* direct syscalls */
     {"rtio_get_counter", &rtio_get_counter},
     {"rtio_log", &rtio_log},
-
-    {"ttl_set_o", &ttl_set_o},
-    {"ttl_set_oe", &ttl_set_oe},
-    {"ttl_set_sensitivity", &ttl_set_sensitivity},
-    {"ttl_get", &ttl_get},
-    {"ttl_clock_set", &ttl_clock_set},
+    {"rtio_output", &rtio_output},
+    {"rtio_input_timestamp", &rtio_input_timestamp},
 
     {"dds_init", &dds_init},
     {"dds_batch_enter", &dds_batch_enter},
     {"dds_batch_exit", &dds_batch_exit},
     {"dds_set", &dds_set},
 
-    {"rt2wb_output", &rt2wb_output},
     {"rt2wb_input", &rt2wb_input},
 
     {"cache_get", &cache_get},
diff --git a/artiq/runtime/rt2wb.c b/artiq/runtime/rt2wb.c
index 6760149c4..ef71f3a91 100644
--- a/artiq/runtime/rt2wb.c
+++ b/artiq/runtime/rt2wb.c
@@ -5,13 +5,6 @@
 #include "rt2wb.h"
 
 
-void rt2wb_output(long long int timestamp, int channel, int addr,
-        unsigned int data)
-{
-    rtio_output(timestamp, channel, addr, data);
-}
-
-
 unsigned int rt2wb_input(int channel)
 {
     unsigned int data;
diff --git a/artiq/runtime/rt2wb.h b/artiq/runtime/rt2wb.h
index d421397f4..158a12d7c 100644
--- a/artiq/runtime/rt2wb.h
+++ b/artiq/runtime/rt2wb.h
@@ -3,10 +3,7 @@
 
 #include "rtio.h"
 
-void rt2wb_output(long long int timestamp, int channel, int addr,
-		unsigned int data);
 unsigned int rt2wb_input(int channel);
-unsigned int rt2wb_input_sync(long long int timeout, int channel);
 
 #endif /* __RT2WB_H */
 
diff --git a/artiq/runtime/rtio.c b/artiq/runtime/rtio.c
index 0670a4e2b..a87bba88b 100644
--- a/artiq/runtime/rtio.c
+++ b/artiq/runtime/rtio.c
@@ -56,8 +56,9 @@ void rtio_output(long long int timestamp, int channel, unsigned int addr,
 }
 
 
-int rtio_input_wait(long long int timeout, int channel)
+long long int rtio_input_timestamp(long long int timeout, int channel)
 {
+    long long int r;
     int status;
 
     rtio_chan_sel_write(channel);
@@ -76,7 +77,17 @@ int rtio_input_wait(long long int timeout, int channel)
         }
         /* input FIFO is empty - keep waiting */
     }
-    return status;
+
+    if (status & RTIO_I_STATUS_OVERFLOW)
+        artiq_raise_from_c("RTIOOverflow",
+                "RTIO input overflow on channel {0}",
+                channel, 0, 0);
+    if (status & RTIO_I_STATUS_EMPTY)
+        return -1;
+
+    r = rtio_i_timestamp_read();
+    rtio_i_re_write(1);
+    return r;
 }
 
 
diff --git a/artiq/runtime/rtio.h b/artiq/runtime/rtio.h
index 9cebb6f2f..1aef9f830 100644
--- a/artiq/runtime/rtio.h
+++ b/artiq/runtime/rtio.h
@@ -19,6 +19,6 @@ void rtio_log(long long int timestamp, const char *format, ...);
 void rtio_log_va(long long int timestamp, const char *format, va_list args);
 void rtio_output(long long int timestamp, int channel, unsigned int address,
         unsigned int data);
-int rtio_input_wait(long long int timeout, int channel);
+long long int rtio_input_timestamp(long long int timeout, int channel);
 
 #endif /* __RTIO_H */
diff --git a/artiq/runtime/ttl.c b/artiq/runtime/ttl.c
deleted file mode 100644
index 603eb2a8c..000000000
--- a/artiq/runtime/ttl.c
+++ /dev/null
@@ -1,42 +0,0 @@
-#include <generated/csr.h>
-
-#include "artiq_personality.h"
-#include "rtio.h"
-#include "ttl.h"
-
-void ttl_set_o(long long int timestamp, int channel, int value)
-{
-    rtio_output(timestamp, channel, 0, value);
-}
-
-void ttl_set_oe(long long int timestamp, int channel, int oe)
-{
-    rtio_output(timestamp, channel, 1, oe);
-}
-
-void ttl_set_sensitivity(long long int timestamp, int channel, int sensitivity)
-{
-    rtio_output(timestamp, channel, 2, sensitivity);
-}
-
-long long int ttl_get(int channel, long long int time_limit)
-{
-    long long int r;
-    int status = rtio_input_wait(time_limit, channel);
-
-    if (status & RTIO_I_STATUS_OVERFLOW)
-        artiq_raise_from_c("RTIOOverflow",
-                "RTIO input overflow on channel {0}",
-                channel, 0, 0);
-    if (status & RTIO_I_STATUS_EMPTY)
-        return -1;
-
-    r = rtio_i_timestamp_read();
-    rtio_i_re_write(1);
-    return r;
-}
-
-void ttl_clock_set(long long int timestamp, int channel, int ftw)
-{
-    rtio_output(timestamp, channel, 0, ftw);
-}
diff --git a/artiq/runtime/ttl.h b/artiq/runtime/ttl.h
deleted file mode 100644
index 9d95a32f2..000000000
--- a/artiq/runtime/ttl.h
+++ /dev/null
@@ -1,10 +0,0 @@
-#ifndef __TTL_H
-#define __TTL_H
-
-void ttl_set_o(long long int timestamp, int channel, int value);
-void ttl_set_oe(long long int timestamp, int channel, int oe);
-void ttl_set_sensitivity(long long int timestamp, int channel, int sensitivity);
-long long int ttl_get(int channel, long long int time_limit);
-void ttl_clock_set(long long int timestamp, int channel, int ftw);
-
-#endif /* __TTL_H */