allow customized units for Motors; do not wait for Motor units PV to connect

slic/devices/general/motor.py

@@ -47,7 +47,7 @@ STATUS_MESSAGES = {
 
 class Motor(Adjustable, SpecConvenienceProgress):
 
-    def __init__(self, pvname, ID=None, name=None, internal=False):
+    def __init__(self, pvname, ID=None, name=None, units=None, internal=False):
         self.pvname = pvname
         self._motor = motor = EpicsMotor(pvname)
 
@@ -61,13 +61,24 @@ class Motor(Adjustable, SpecConvenienceProgress):
         )
 
         ID = ID or pvname
-        units = self.pvs.units.value
         super().__init__(ID, name=name, units=units, internal=internal)
 
         self.status = None
         self.status_message = None
 
 
+    @property
+    def units(self):
+        units = self._units
+        if units is not None:
+            return units
+        return self.pvs.units.value
+
+    @units.setter
+    def units(self, value):
+        self._units = value
+
+
     def get_current_value(self, readback=True, pos_type="user"):
         check_pos_type(pos_type)
         kwargs = POS_TYPE_KWARGS[pos_type]