diff --git a/cosimulation/icarus/myhdl.c b/cosimulation/icarus/myhdl.c
new file mode 100644
index 00000000..108a4cec
--- /dev/null
+++ b/cosimulation/icarus/myhdl.c
@@ -0,0 +1,293 @@
+#include <stdlib.h>
+#include <unistd.h>
+#include <assert.h>
+#include "vpi_user.h"
+
+#define MAXLINE 4096
+#define MAXWIDTH 10
+
+typedef int PLI_INT32;
+typedef char PLI_BYTE8;
+
+static int rpipe;
+static int wpipe;
+
+static vpiHandle from_myhdl_systf_handle = NULL;
+
+typedef struct to_myhdl_data {
+  vpiHandle systf_handle;
+  short int sync_flag;
+} s_to_myhdl_data, *p_to_myhdl_data;
+
+/* prototypes */
+static PLI_INT32 from_myhdl_calltf(PLI_BYTE8 *user_data);
+static PLI_INT32 to_myhdl_calltf(PLI_BYTE8 *user_data);
+static PLI_INT32 to_myhdl_sensitivity_callback(p_cb_data cb_data);
+static PLI_INT32 to_myhdl_write_callback(p_cb_data cb_data);
+
+static int init_pipes();
+
+static int init_pipes()
+{
+  char *w;
+  char *r;
+
+  static int init_pipes_flag = 0;
+
+  if (init_pipes_flag) {
+    vprintf("INFO: pipes already initialized\n");
+    return(0);
+  }
+
+  if ((w = getenv("MYHDL_TO_PIPE")) == NULL) {
+    vpi_printf("ERROR: no write pipe to myhdl\n");
+    vpi_control(vpiFinish, 1);  /* abort simulation */
+    return(0);
+  }
+  if ((r = getenv("MYHDL_FROM_PIPE")) == NULL) {
+    vpi_printf("ERROR: no read pipe from myhdl\n");
+    vpi_control(vpiFinish, 1);  /* abort simulation */
+    return(0);
+  }
+  wpipe = atoi(w);
+  rpipe = atoi(r);
+  init_pipes_flag = 1;
+  return (0);
+}
+
+static PLI_INT32 from_myhdl_calltf(PLI_BYTE8 *user_data)
+{
+  vpiHandle net_iter, net_handle;
+  vpiHandle cb_h;
+  s_vpi_time current_time;
+  char buf[MAXLINE];
+  char s[MAXWIDTH];
+  int n;
+
+  static int from_myhdl_flag = 0;
+
+  if (from_myhdl_flag) {
+    vpi_printf("ERROR: $from_myhdl called more than once\n");
+    vpi_control(vpiFinish, 1);  /* abort simulation */
+    return(0);
+  }
+  from_myhdl_flag = 1;
+
+  init_pipes();
+
+  vpi_printf("Hello from $from_myhdl %d %d\n", rpipe, wpipe);
+  from_myhdl_systf_handle = vpi_handle(vpiSysTfCall, NULL);
+  net_iter = vpi_iterate(vpiArgument, from_myhdl_systf_handle);
+
+  current_time.type = vpiSimTime;
+  vpi_get_time(NULL, &current_time);
+  sprintf(buf, "FROM %x%08x ", current_time.high, current_time.low);
+
+  while ((net_handle = vpi_scan(net_iter)) != NULL) {
+    strcat(buf, vpi_get_str(vpiName, net_handle));
+    strcat(buf, " ");
+    sprintf(s, "%d ", vpi_get(vpiSize, net_handle));
+    strcat(buf, s);
+  }
+  write(wpipe, buf, strlen(buf));
+
+  if ((n = read(rpipe, buf, MAXLINE)) == 0) {
+    vpi_printf("Info: myhdl down\n");
+    vpi_control(vpiFinish, 1);  /* abort simulation */
+    return(0);
+  }
+  buf[n] = '\0';
+  return(0);
+
+
+}
+
+static PLI_INT32 to_myhdl_calltf(PLI_BYTE8 *user_data)
+{
+  vpiHandle systf_handle, net_iter, net_handle;
+  vpiHandle cb_h;
+  char buf[MAXLINE];
+  char s[MAXWIDTH];
+  int n;
+  s_vpi_time current_time;
+  s_cb_data cb_data_s;
+  s_vpi_time time_s;
+  s_vpi_value value_s;
+  p_to_myhdl_data to_myhdl_data;
+  static int to_myhdl_flag = 0;
+
+  if (to_myhdl_flag) {
+    vpi_printf("ERROR: $to_myhdl called more than once\n");
+    vpi_control(vpiFinish, 1);  /* abort simulation */
+    return(0);
+  }
+  to_myhdl_flag = 1;
+
+  init_pipes();
+
+  vpi_printf("Hello from $to_myhdl %d %d\n", rpipe, wpipe);
+  systf_handle = vpi_handle(vpiSysTfCall, NULL);
+
+  to_myhdl_data = (p_to_myhdl_data)malloc(sizeof(s_to_myhdl_data));
+  to_myhdl_data->systf_handle = systf_handle;
+  to_myhdl_data->sync_flag = 0;
+ 
+  /* setup sensitivity callback */
+  time_s.type = vpiSuppressTime;
+  value_s.format = vpiSuppressVal;
+  cb_data_s.reason = cbValueChange;
+  cb_data_s.user_data = (PLI_BYTE8 *)to_myhdl_data;
+  cb_data_s.cb_rtn = to_myhdl_sensitivity_callback;
+  cb_data_s.time = &time_s;
+  cb_data_s.value = NULL;
+
+  net_iter = vpi_iterate(vpiArgument, systf_handle);
+
+  current_time.type = vpiSimTime;
+  vpi_get_time(NULL, &current_time);
+  sprintf(buf, "TO %x%08x ", current_time.high, current_time.low);
+
+  while ((net_handle = vpi_scan(net_iter)) != NULL) {
+    cb_data_s.obj = net_handle;
+    vpi_register_cb(&cb_data_s);
+    strcat(buf, vpi_get_str(vpiName, net_handle));
+    strcat(buf, " ");
+    sprintf(s, "%d ", vpi_get(vpiSize, net_handle));
+    strcat(buf, s);
+  }
+  write(wpipe, buf, strlen(buf));
+
+  if ((n = read(rpipe, buf, MAXLINE)) == 0) {
+    vpi_printf("Info: myhdl down\n");
+    vpi_control(vpiFinish, 1);  /* abort simulation */
+    return(0);
+  }
+  buf[n] = '\0';
+
+  // register write callback by default at time 0 //
+  vpi_printf("register cb\n");
+  to_myhdl_data->sync_flag = 1;
+  time_s.type = vpiSimTime;
+  time_s.high = 0;
+  time_s.low = 0;
+  cb_data_s.reason = cbReadWriteSynch;
+  cb_data_s.user_data = (PLI_BYTE8 *)to_myhdl_data;
+  cb_data_s.cb_rtn = to_myhdl_write_callback;
+  cb_data_s.obj = NULL;
+  cb_data_s.time = &time_s;
+  cb_data_s.value = NULL;
+  vpi_register_cb(&cb_data_s);
+
+  return(0);
+
+}
+
+
+static PLI_INT32 to_myhdl_sensitivity_callback(p_cb_data cb_data)
+{
+  vpiHandle cb_h;
+  s_cb_data cb_data_s;
+  s_vpi_time time_s;
+  p_to_myhdl_data to_myhdl_data;
+  vpiHandle net_handle;
+
+  to_myhdl_data = (p_to_myhdl_data)cb_data->user_data;
+  vpi_printf("sens triggered\n");
+  if (!to_myhdl_data->sync_flag) {
+    vpi_printf("register cb\n");
+    to_myhdl_data->sync_flag = 1;
+    time_s.type = vpiSimTime;
+    time_s.high = 0;
+    time_s.low = 0;
+    cb_data_s.reason = cbReadWriteSynch;
+    cb_data_s.user_data = (PLI_BYTE8 *)to_myhdl_data;
+    cb_data_s.cb_rtn = to_myhdl_write_callback;
+    cb_data_s.obj = NULL;
+    cb_data_s.time = &time_s;
+    cb_data_s.value = NULL;
+    vpi_register_cb(&cb_data_s);
+  }
+  return(0);
+}
+
+static PLI_INT32 to_myhdl_write_callback(p_cb_data cb_data)
+{
+  vpiHandle systf_handle;
+  vpiHandle net_iter, net_handle;
+  vpiHandle reg_iter, reg_handle;
+  p_to_myhdl_data to_myhdl_data;
+  s_vpi_time current_time;
+  s_vpi_value value_s;
+  char buf[MAXLINE];
+  int n;
+
+  static int start_flag = 1;
+
+  vpi_printf("write callback\n");
+
+  if (start_flag) {
+    start_flag = 0;
+    write(wpipe, "START", 5);
+    if ((n = read(rpipe, buf, MAXLINE)) == 0) {
+      vpi_printf("Info: myhdl down\n");
+      vpi_control(vpiFinish, 1);  /* abort simulation */
+      buf[n] = '\0';
+    }
+  }
+
+  to_myhdl_data = (p_to_myhdl_data)cb_data->user_data;
+  vpi_printf("sync flag: %d\n", to_myhdl_data->sync_flag);
+  to_myhdl_data->sync_flag = 0;
+  systf_handle = to_myhdl_data->systf_handle;
+
+  net_iter = vpi_iterate(vpiArgument, systf_handle);
+  buf[0] = '\0';
+  current_time.type = vpiSimTime;
+  vpi_get_time(systf_handle, &current_time);
+  sprintf(buf, "%x%08x ", current_time.high, current_time.low);
+  value_s.format = vpiHexStrVal;
+  while ((net_handle = vpi_scan(net_iter)) != NULL) {
+    vpi_get_value(net_handle, &value_s);
+    strcat(buf, value_s.value.str);
+    strcat(buf, " ");
+  }
+  write(wpipe, buf, strlen(buf));
+  if ((n = read(rpipe, buf, MAXLINE)) == 0) {
+    vpi_printf("Info: myhdl down\n");
+    vpi_control(vpiFinish, 1);  /* abort simulation */
+    return(0);
+  }
+  buf[n] = '\0';
+  vpi_printf("C Read %d %s\n", n, buf);
+  reg_iter = vpi_iterate(vpiArgument, from_myhdl_systf_handle);
+  while ((reg_handle = vpi_scan(reg_iter)) != NULL) {
+    assert(sscanf(buf, "%s", value_s.value.str));
+    vpi_put_value(reg_handle, &value_s, NULL, vpiNoDelay);
+  }
+
+  return(0);
+}
+
+
+
+void myhdl_register()
+{
+  s_vpi_systf_data tf_data;
+
+  tf_data.type      = vpiSysTask;
+  tf_data.tfname    = "$to_myhdl";
+  tf_data.calltf    = to_myhdl_calltf;
+  tf_data.compiletf = NULL;
+  tf_data.sizetf    = NULL;
+  tf_data.user_data = "$to_myhdl";
+  vpi_register_systf(&tf_data);
+
+  tf_data.type      = vpiSysTask;
+  tf_data.tfname    = "$from_myhdl";
+  tf_data.calltf    = from_myhdl_calltf;
+  tf_data.compiletf = NULL;
+  tf_data.sizetf    = NULL;
+  tf_data.user_data = "$from_myhdl";
+  vpi_register_systf(&tf_data);
+
+}
diff --git a/cosimulation/icarus/myhdl_table.c b/cosimulation/icarus/myhdl_table.c
new file mode 100644
index 00000000..f74e214f
--- /dev/null
+++ b/cosimulation/icarus/myhdl_table.c
@@ -0,0 +1,8 @@
+# include "vpi_user.h"
+
+extern void myhdl_register();
+
+void (*vlog_startup_routines[])() = {
+      myhdl_register,
+      0
+};