Added interpose driver from DLS

Added a low-level interpose driver to allow usage of stream devices.

db/turboPmac.db

@@ -16,4 +16,18 @@ record(longout, "$(INSTR)$(M):ReadConfig") {
     field(DTYP, "asynInt32")
     field(OUT, "@asyn($(CONTROLLER),$(AXIS),1) READ_CONFIG")
     field(PINI, "NO")
-}
+}
+
+# PMAC controllers can be "flushed" by setting a certain bit. This empties all
+# communication buffers. Once the flush is done, the controller acknowledges
+# this by sending an echo character. This procedure can take up to 10 ms (see 
+# Turbo PMAC User Manual, p. 414) and should therefore not be done as part of
+# "normal" communications (like the original pmacAsynIPPort driver from DLS 
+# does). The SINQ driver for the Turbo PMAC controller therefore offers this PV
+# in order to manually trigger a controller flush by writing any value to this PV.
+record(longout, "$(INSTR)FlushHardware") {
+    field(DTYP, "asynInt32")
+    field(OUT, "@asyn($(CONTROLLER),$(AXIS),1) FLUSH_HARDWARE")
+    field(PINI, "NO")
+    field(VAL, "1")
+}