diff --git a/adiv5-swd.rb b/adiv5-swd.rb
index 3de5f0d..ac1dd52 100644
--- a/adiv5-swd.rb
+++ b/adiv5-swd.rb
@@ -54,7 +54,7 @@ def read(port, addr, opt={})
     if !opt[:count]
       reply = @drv.transfer(req)
     else
-      req[:count] = readcount
+      req[:val] = readcount
       reply = @drv.transfer_block(req)
     end
 
diff --git a/nrf51.rb b/nrf51.rb
index 0009f03..600b6d4 100644
--- a/nrf51.rb
+++ b/nrf51.rb
@@ -70,6 +70,12 @@ def mass_erase
         sleep 0.01
       end
 
+      self.ERASEUICR = 1
+      while !self.READY.ready
+        Log(:nrf51, 1){ "waiting for UICR erase completion" }
+        sleep 0.01
+      end
+
       self.CONFIG.WEN = :REN  # enable read
 
       if self.CONFIG.WEN != :REN
diff --git a/swd-bitbang.rb b/swd-bitbang.rb
index eb5c1ec..8488fd2 100644
--- a/swd-bitbang.rb
+++ b/swd-bitbang.rb
@@ -80,7 +80,7 @@ def transfer(req)
         # reads to the AP are posted, so we need to get the result in a
         # separate transfer.
         if req[:port] == :ap
-          rdbufret = transfer(dir: :read, port: :dp, addr: Adiv5Swd::RDBUFF)
+          rdbufret = transfer(op: :read, port: :dp, addr: Adiv5Swd::RDBUFF)
           ret[:ack] = rdbufret[:ack]
           data = rdbufret[:val]
         end
@@ -109,4 +109,7 @@ def calc_parity(data)
   def hexify(str)
     str.unpack('C*').map{|e| "%02x" % e}.join(' ')
   end
+
+  def flush!
+  end
 end