diff --git a/site_ansto/motor_dmc2280.c b/site_ansto/motor_dmc2280.c
index 38dde655..813d2576 100644
--- a/site_ansto/motor_dmc2280.c
+++ b/site_ansto/motor_dmc2280.c
@@ -198,9 +198,6 @@ struct __MoDriv {
   pNWTimer state_timer; /**< motor state timer */
   SConnection *trace;
   int posit_count;
-#ifdef POSIT_COUNTS
-  long long* posit_array;
-#endif
   double* positions;
   int variables;
 #if defined(STATE_TRACE) && (STATE_TRACE > 0)
@@ -208,6 +205,8 @@ struct __MoDriv {
   char state_trace_text[STATE_TRACE][CMDLEN];
   struct timeval state_trace_time[STATE_TRACE];
 #endif
+  int bias_bits; /**< number of bits to mask */
+  int bias_bias; /**< bias to add to encoder value */
 };
 
 int DMC2280MotionControl = 1; /* defaults to enabled */
@@ -283,70 +282,6 @@ static int DMC2280Halt(void *pData);
 static int DMC2280SetPar(void *pData, SConnection *pCon,
     char *name, float newValue);
 
-#ifdef POSIT_COUNTS
-static bool check_posits(pDMC2280Driv self) {
-  char line[CMDLEN];
-  int missing = 0;
-  int direction = 0;
-  int i;
-
-  if (self->posit_count < 2) {
-    snprintf(line, ERRLEN, "Insufficient positions on motor '%s': %d",
-        self->name, self->posit_count);
-    SICSLogWrite(line,eError);
-    return false;
-  }
-  for (i = 0; i < self->posit_count; ++i)
-    if (self->posit_array[i] < 0)
-      ++missing;
-  if (missing) {
-    snprintf(line, ERRLEN, "Missing positions on motor '%s': %d",
-        self->name, missing);
-    SICSLogWrite(line,eError);
-    return false;
-  }
-  for (i = 1; i < self->posit_count; ++i) {
-    if (i == 1) {
-      if (self->posit_array[i] > self->posit_array[i - 1])
-        direction = 1;
-      else if (self->posit_array[i] < self->posit_array[i - 1])
-        direction = -1;
-      else
-        direction = 0;
-    }
-    if (direction == 0) {
-      snprintf(line, ERRLEN, "Position order on motor '%s' : %d",
-          self->name, i);
-      SICSLogWrite(line,eError);
-    }
-    else {
-      switch (direction) {
-        case -1:
-          if (!(self->posit_array[i] < self->posit_array[i - 1])) {
-            direction = 0;
-          }
-          break;
-        case 1:
-          if (!(self->posit_array[i] > self->posit_array[i - 1])) {
-            direction = 0;
-          }
-          break;
-      }
-    }
-  }
-  if (direction != 0)
-    return true;
-  for (i = 0; i < self->posit_count; ++i) {
-    snprintf(line, ERRLEN, "Position %2d motor '%s' : %lld",
-        i + 1,
-        self->name,
-        self->posit_array[i]);
-    /* TODO log me */
-  }
-  return false;
-}
-#endif
-
 static bool check_positions(pDMC2280Driv self) {
   char line[CMDLEN];
   int missing = 0;
@@ -452,88 +387,6 @@ static double count2unit(pDMC2280Driv self, long long counts) {
   return fPos;
 }
 
-#ifdef POSIT_COUNTS
-static long long posit2count(pDMC2280Driv self, double target) {
-  double absolute;
-  long long result;
-  if (self->abs_encoder == 0) {
-    char line[CMDLEN];
-    snprintf(line, CMDLEN, "posit2count motor %s has no absolute encoder",
-        self->name);
-    SICSLogWrite(line, eStatus);
-    return -1;
-  }
-  if (!check_posits(self))
-    return -1;
-
-  int i = ((int) target) - 1;
-  if (i < 0) {
-    i = 0;
-  } else if (i > self->posit_count - 2) {
-    i = self->posit_count - 2;
-  }
-  absolute = (double)self->posit_array[i]
-    + ((double)target - ((double)i + 1)) *
-    ((double)self->posit_array[i + 1] - self->posit_array[i]);
-  if (absolute > 0)
-    result = (int) (absolute + 0.5);
-  else if (absolute < 0)
-    result = (int) (absolute - 0.5);
-  else
-    result = (int) absolute;
-  if (self->debug) {
-    char line[CMDLEN];
-    snprintf(line, CMDLEN, "posit2count Rounding %f to %lld", absolute, result);
-    SICSLogWrite(line, eStatus);
-  }
-  return result;
-}
-
-static double count2posit(pDMC2280Driv self, long long counts) {
-  int i, j;
-  double fPos;
-  if (self->abs_encoder == 0) {
-    char line[CMDLEN];
-    snprintf(line, CMDLEN, "count2posit motor %s has no absolute encoder",
-        self->name);
-    SICSLogWrite(line, eStatus);
-    return 0;
-  }
-  if (!check_posits(self))
-    return 0;
-
-  if (self->posit_array[0] < self->posit_array[1]) {
-    for (i = 1; i < self->posit_count - 1; ++i) {
-      if (counts < self->posit_array[i]) {
-        break;
-      }
-    }
-  }
-  else {
-    for (i = 1; i < self->posit_count - 1; ++i) {
-      if (counts > self->posit_array[i]) {
-        break;
-      }
-    }
-  }
-  --i;
-  j = i + 1;
-  fPos = (double) j +
-    ((double)counts - self->posit_array[i]) /
-    ((double)self->posit_array[j] - self->posit_array[i]);
-  return fPos;
-}
-
-static double unit2posit(pDMC2280Driv self, double target) {
-  return count2posit(self, unit2count(self, target));
-}
-
-static double posit2unit(pDMC2280Driv self, double target) {
-  return count2unit(self, posit2count(self, target));
-}
-
-#else
-
 static double unit2posit(pDMC2280Driv self, double target) {
   int i, j;
   double fPos;
@@ -584,8 +437,6 @@ static double count2posit(pDMC2280Driv self, long long counts) {
   return unit2posit(self, count2unit(self, counts));
 }
 
-#endif
-
 /** \brief Convert axis speed in physical units to
  * motor speed in steps/sec.
  *
@@ -1026,7 +877,10 @@ static int readAbsEnc(pDMC2280Driv self, long *pos) {
   if (FAILURE == DMC_SendReceive(self, cmd, reply))
     return FAILURE;
 
-  *pos = atol(reply);
+  long iCounts = atol(reply);
+  if (self->bias_bits > 0 && self->bias_bias != 0)
+    iCounts = (iCounts + self->bias_bias) & ((1 << self->bias_bits) - 1);
+  *pos = iCounts;
   return SUCCESS;
 }
 
@@ -1446,6 +1300,8 @@ static int rspStatus(pDMC2280Driv self, const char* text) {
   }
   self->currFlags = iFlags;
   self->currSteps = iSteps;
+  if (self->bias_bits > 0 && self->bias_bias != 0)
+    iCounts = (iCounts + self->bias_bias) & ((1 << self->bias_bits) - 1);
   self->currCounts = iCounts;
   self->currPosition = motPosit(self);
   self->thread0 = iXQ0;
@@ -1777,7 +1633,6 @@ static void DMCState_Unknown(pDMC2280Driv self, pEvtEvent event) {
       /* handle pending message event */
       if (self->waitResponse) {
         self->subState = 0;
-        /* FIXME: FIXME_DOUG */
         return;
       }
       /* Set speed */
@@ -2521,7 +2376,7 @@ static void DMCState_Moving(pDMC2280Driv self, pEvtEvent event) {
     case eCommandEvent:
       switch (event->event.cmd.cmd_type) {
         case CMD_RUN:
-          /* TODO: FIXME RUN command while running */
+          /* RUN command while running */
           if (self->driver_status == HWIdle)
             self->driver_status = HWBusy;
           self->run_flag = 1;
@@ -2966,7 +2821,7 @@ static void DMC2280Error(void *pData, int *iCode, char *error, int errLen){
       strncpy(error, self->dmc2280Error, (size_t)errLen);
       break;
     default:
-      /* FIXME What's the default */
+      /* What's the default */
       snprintf(error, (size_t)errLen, "Unknown Motor Error: %d", self->errorCode);
       break;
   }
@@ -3143,6 +2998,14 @@ static int DMC2280GetPar(void *pData, char *name,
     *fValue = self->backlash_offset;
     return 1;
   }
+  if(strcasecmp(name,"bias_bias") == 0) {
+    *fValue = self->bias_bias;
+    return 1;
+  }
+  if(strcasecmp(name,"bias_bits") == 0) {
+    *fValue = self->bias_bits;
+    return 1;
+  }
   if (self->posit_count > 0) {
     if (strncasecmp(name, "posit_", 6) == 0 && isdigit(name[6])) {
       int index;
@@ -3453,26 +3316,39 @@ static int DMC2280SetPar(void *pData, SConnection *pCon,
     self->fUpper = newValue;
     return 1;
   }
-  if (self->abs_encoder && strcasecmp("stepsPerX", name) == 0) {
+  if (strcasecmp("stepsPerX", name) == 0) {
     /* Debug Managers only */
     if (!(self->debug && SCMatchRights(pCon, usMugger)))
       return 0;
     self->stepsPerX = newValue;
     return 1;
   }
-  if (self->debug && strcasecmp("cntsPerX", name) == 0) {
+  if (self->abs_encoder && strcasecmp("cntsPerX", name) == 0) {
     /* Debug Managers only */
     if (!(self->debug && SCMatchRights(pCon, usMugger)))
       return 0;
     self->cntsPerX = newValue;
     return 1;
   }
-
+  if (self->abs_encoder && strcasecmp("bias_bias", name) == 0) {
+    /* Debug Managers only */
+    if (!(self->debug && SCMatchRights(pCon, usMugger)))
+      return 0;
+    self->bias_bias = newValue;
+    return 1;
+  }
+  if (self->abs_encoder && strcasecmp("bias_bits", name) == 0) {
+    /* Debug Managers only */
+    if (!(self->debug && SCMatchRights(pCon, usMugger)))
+      return 0;
+    self->bias_bits = newValue;
+    return 1;
+  }
   /* XXX Maybe move this to a configuration parameter.*/
   /* Set home, managers only. Users should set softposition */
   if(strcasecmp(name, HOME) == 0) {
     /* Debug Managers only */
-    if(!(self->debug && SCMatchRights(pCon,usMugger)))
+    if(!SCMatchRights(pCon,usMugger))
       return 1;
     else {
       if ( (self->fLower - newValue) > FLT_EPSILON) {
@@ -3496,9 +3372,6 @@ static int DMC2280SetPar(void *pData, SConnection *pCon,
         index = strtol(&name[6], NULL, 10);
         if (index < 1 || index > self->posit_count)
           return 0;
-#ifdef POSIT_COUNTS
-        self->posit_array[index - 1] = newValue;
-#endif
         self->positions[index - 1] = count2unit(self, newValue);
         return 1;
       }
@@ -3641,12 +3514,6 @@ static void KillDMC2280(/*@only@*/void *pData){
     AsyncUnitDestroy(self->asyncUnit);
     self->asyncUnit = NULL;
   }
-#ifdef POSIT_COUNTS
-  if (self->posit_array) {
-    free(self->posit_array);
-    self->posit_array = NULL;
-  }
-#endif
   if (self->positions) {
     free(self->positions);
     self->positions = 0;
@@ -3929,37 +3796,44 @@ MotorDriver *CreateDMC2280(SConnection *pCon, char *motor, char *params) {
         pNew->creep_precision = -pNew->creep_precision;
     }
 
-    if ((pPtr=getParam(pCon, interp, params,"posit_count",_OPTIONAL)) == NULL)
-      pNew->posit_count = 0;
+    /* BIAS for encoder - add this to value read */
+    if ((pPtr=getParam(pCon, interp, params,"bias_bias",_OPTIONAL)) == NULL)
+      pNew->bias_bias = 0;
     else {
-      sscanf(pPtr,"%d",&(pNew->posit_count));
-      if (pNew->posit_count < 1 || pNew->posit_count > 99) {
-        snprintf(pError, ERRLEN, "Invalid posit_count on motor '%s': %d", motor,
-            pNew->posit_count);
-        SCWrite(pCon,pError,eError);
-        pNew->posit_count = 0;
-      }
-      else {
-        int i;
-        char line[80];
-#ifdef POSIT_COUNTS
-        pNew->posit_array = malloc(pNew->posit_count * sizeof(*pNew->posit_array));
-#endif
-        pNew->positions = malloc(pNew->posit_count * sizeof(*pNew->positions));
-        for (i = 0; i < pNew->posit_count; ++i) {
-          snprintf(line, 80, "posit_%d", i + 1);
-          if ((pPtr=getParam(pCon, interp, params,line,_OPTIONAL)) == NULL) {
-#ifdef POSIT_COUNTS
-            pNew->posit_array[i] = -1;
-#endif
-            pNew->positions[i] = 0.0;
-          }
-          else {
-#ifdef POSIT_COUNTS
-            pNew->posit_array[i] = strtol(pPtr, NULL, 10);
-#endif
-            pNew->positions[i] = count2unit(pNew, strtol(pPtr, NULL, 10));
-          }
+      sscanf(pPtr, "%d", &(pNew->bias_bias));
+    }
+
+    /* BIAS for encoder - mask this many bits */
+    if ((pPtr=getParam(pCon, interp, params,"bias_bits",_OPTIONAL)) == NULL)
+      pNew->bias_bits = 0.0;
+    else {
+      sscanf(pPtr, "%d", &(pNew->bias_bits));
+      if (pNew->bias_bits < 0)
+        pNew->bias_bits = -pNew->bias_bits;
+    }
+  }
+
+  if ((pPtr=getParam(pCon, interp, params,"posit_count",_OPTIONAL)) == NULL)
+    pNew->posit_count = 0;
+  else {
+    sscanf(pPtr,"%d",&(pNew->posit_count));
+    if (pNew->posit_count < 1 || pNew->posit_count > 99) {
+      snprintf(pError, ERRLEN, "Invalid posit_count on motor '%s': %d", motor,
+          pNew->posit_count);
+      SCWrite(pCon,pError,eError);
+      pNew->posit_count = 0;
+    }
+    else {
+      int i;
+      char line[80];
+      pNew->positions = malloc(pNew->posit_count * sizeof(*pNew->positions));
+      for (i = 0; i < pNew->posit_count; ++i) {
+        snprintf(line, 80, "posit_%d", i + 1);
+        if ((pPtr=getParam(pCon, interp, params,line,_OPTIONAL)) == NULL) {
+          pNew->positions[i] = 0.0;
+        }
+        else {
+          pNew->positions[i] = count2unit(pNew, strtol(pPtr, NULL, 10));
         }
       }
     }
@@ -4217,12 +4091,6 @@ int DMC2280Action(SConnection *pCon, SicsInterp *pSics, void *pData,
       if (self->posit_count > 0) {
         self->posit_count = 0;
       }
-#ifdef POSIT_COUNTS
-      if (self->posit_array) {
-        free(self->posit_array);
-        self->posit_array = NULL;
-      }
-#endif
       if (self->positions) {
         free(self->positions);
         self->positions = NULL;
@@ -4236,15 +4104,9 @@ int DMC2280Action(SConnection *pCon, SicsInterp *pSics, void *pData,
       }
       self->posit_count = argc - 2;
       self->positions = malloc(self->posit_count * sizeof(*self->positions));
-#ifdef POSIT_COUNTS
-      self->posit_array = malloc(self->posit_count * sizeof(*self->posit_array));
-#endif
       int i;
       for (i = 0; i < self->posit_count; ++i) {
         self->positions[i] = strtod(argv[i + 2], NULL);
-#ifdef POSIT_COUNTS
-        self->posit_array[i] = unit2count(self, self->positions[i]);
-#endif
       }
       return 1;
     }