diff --git a/site_ansto/hardsup/sct_modbusprot.c b/site_ansto/hardsup/sct_modbusprot.c
index bb0a7376..88197c92 100644
--- a/site_ansto/hardsup/sct_modbusprot.c
+++ b/site_ansto/hardsup/sct_modbusprot.c
@@ -6,11 +6,71 @@
 #include <ascon.i>
 #include <dynstring.h>
 #include <stdbool.h>
+#include <math.h>
 
 static int dbgprintf(char* fmtstr, ...);
 static int dbgprintx(const char* msg, const unsigned char* cp, int blen);
 static unsigned int debug_modbus = 1;
 
+/*-------------------------------------------------------------------------*/
+/* IEEE code copied from psi/modbus.c */
+static void double2ieee(double input, char ieee[4]) {
+
+/* convert double to IEEE 32 bit floating number (denormalized numbers are considered as zero) */
+
+  long mantissa;
+  int exponent;
+
+  if (input == 0) {
+    ieee[0]= 0;
+    ieee[1]= 0;
+    ieee[2]= 0;
+    ieee[3]= 0;
+  } else {
+    mantissa = 0x1000000 * (frexp(fabs(input), &exponent));
+    exponent = exponent - 1 + 127;
+    if (exponent < 0) {
+      exponent = 0;
+    } else if (exponent > 0xFE) {
+      exponent = 0xFE;
+    }
+    if (input < 0) {
+      ieee[0] = 0x80 | (exponent >> 1);
+    } else {
+      ieee[0] = exponent >> 1;
+    }
+    ieee[1] = (exponent & 1) << 7 | ((mantissa & 0x7F0000) >> 16);
+    ieee[2] = (mantissa & 0xFF00) >> 8;
+    ieee[3] = mantissa & 0xFF;
+  }
+  return;
+}
+
+/*-------------------------------------------------------------------------*/
+static double ieee2double(char ieee[4]) {
+
+/* IEEE 32 bit floating number to double (denormalized numbers are considered as zero) */
+
+  long mantissa;
+  double output;
+  int exponent;
+  
+  mantissa = ((ieee[1] << 16) & 0x7FFFFF) 
+           | ((ieee[2] <<  8) & 0xFF00)
+           | ((ieee[3]      ) & 0xFF);
+  
+  exponent = (ieee[0] & 0x7F) * 2 + ((ieee[1] >> 7) & 1); /* raw exponent */
+  if (exponent == 0 && mantissa == 0) {
+    return 0.0;
+  }
+  output = ldexp(mantissa, -23) + 1.0;
+  if (ieee[0] & 0x80) {
+    output = -output;
+  }
+  return output * ldexp(1, exponent - 127);
+}
+/*-------------------------------------------------------------------------*/
+
 /** @brief encode modbus request
 * TODO: clean me up
 */
@@ -71,19 +131,22 @@ int ModbusWriteStart(Ascon *a) {
   if (cmd == 16) { /* write registers */
     buff = endp + 1;
     if (do_float) {
-      union { unsigned char v[4]; float val; } u;
-      u.val = strtof(buff, &endp);
+      struct { char v[4]; } ieee;        /* big endian */
+      double val = strtod(buff, &endp);
       if (endp == buff) {
-        dbgprintf("modbus-er: Bad value: %f from %s\n", u.val, buff);
+        dbgprintf("modbus-er: Bad value: %f from %s\n", val, buff);
         a->state = AsconIdle;
         AsconError(a, "Bad value", 0);
         return 0;
       }
+      double2ieee(val, ieee.v);
+      dbgprintf("strtod:%f\n", val);
+      dbgprintx("double2ieee", (unsigned char*)ieee.v, 4);
       temp[idx++] = 4; /* byte count */
-      temp[idx++] = u.v[1];
-      temp[idx++] = u.v[0];
-      temp[idx++] = u.v[3];
-      temp[idx++] = u.v[2];
+      temp[idx++] = ieee.v[2]; /* watlow RUI specific byte ordering */
+      temp[idx++] = ieee.v[3];
+      temp[idx++] = ieee.v[0];
+      temp[idx++] = ieee.v[1];
     } else {
       unsigned int val;
       val = strtoul(buff, &endp, 10);
@@ -137,12 +200,16 @@ int ModbusReading(Ascon *a) {
           rlen = snprintf(temp, 64, "%d", (((unsigned int)cp[9]) << 8) + (unsigned int)cp[10]);
         }
         else if (cp[7] == 3 && cp[8] == 4) {
-          union { unsigned char v[4]; float val; } u;
-          u.v[1] = cp[9];
-          u.v[0] = cp[10];
-          u.v[3] = cp[11];
-          u.v[2] = cp[12];
-          rlen = snprintf(temp, 64, "%g", u.val);
+          struct { char v[4]; } ieee;
+          double val;
+          ieee.v[2] = cp[9]; /* watlow RUI specific byte ordering */
+          ieee.v[3] = cp[10];
+          ieee.v[0] = cp[11];
+          ieee.v[1] = cp[12];
+          val = ieee2double(ieee.v);
+          dbgprintx("rawhex", (unsigned char*)&cp[9], 4);
+          dbgprintf("ieee2double:%f\n", val);
+          rlen = snprintf(temp, 64, "%g", val);
         }
         else if (cp[7] == 16 && cp[11] == 1) {
           rlen = snprintf(temp, 64, "OK int");