jtag_stm32: Fix incorrect handling of registers.

The STM32F10xxx has two serially connected JTAG TAPs, the boundary scan tap
(5 bits) and the Cortex-M3 TAP (4 bits). See UM 31.5 "STM32F10xxx JTAG TAP
connection" for details.
Due to this, we need to ignore the last bit of each data shift (and we
currently ignore the 5 bits of the boundary scan tap).

diff --git a/decoders/jtag_stm32/pd.py b/decoders/jtag_stm32/pd.py
index f2dd3c7726dfce97e6a5040204be57afac2b8547..51c910defd03c75f7775c636964339651624f83c 100644 (file)
--- a/decoders/jtag_stm32/pd.py
+++ b/decoders/jtag_stm32/pd.py
@@ -1,7 +1,7 @@
 ##
 ## This file is part of the libsigrokdecode project.
 ##
-## Copyright (C) 2012 Uwe Hermann <uwe@hermann-uwe.de>
+## Copyright (C) 2012-2015 Uwe Hermann <uwe@hermann-uwe.de>
 ##
 ## This program is free software; you can redistribute it and/or modify
 ## it under the terms of the GNU General Public License as published by
@@ -183,7 +183,11 @@ class Decoder(srd.Decoder):
 
         self.ss, self.es = ss, es
 
-        # self.put(self.ss, self.es, self.out_ann, [0, [cmd + ' / ' + val]])
+        # The STM32F10xxx has two serially connected JTAG TAPs, the
+        # boundary scan tap (5 bits) and the Cortex-M3 TAP (4 bits).
+        # See UM 31.5 "STM32F10xxx JTAG TAP connection" for details.
+        # Due to this, we need to ignore the last bit of each data shift.
+        val = val[:-1]
 
         # State machine
         if self.state == 'IDLE':
@@ -191,9 +195,10 @@ class Decoder(srd.Decoder):
             if cmd != 'IR TDI':
                 return
             # Switch to the state named after the instruction, or 'UNKNOWN'.
-            # Ignore bits other than IR[3:0]. While the IR register is only
-            # 4 bits in size, some programs (e.g. OpenOCD) might fill in a
-            # few more (dummy) bits. OpenOCD makes IR at least 8 bits long.
+            # The STM32F10xxx has two serially connected JTAG TAPs, the
+            # boundary scan tap (5 bits) and the Cortex-M3 TAP (4 bits).
+            # See UM 31.5 "STM32F10xxx JTAG TAP connection" for details.
+            # Currently we only care about the latter and use IR[3:0].
             self.state = ir.get(val[-4:], ['UNKNOWN', 0])[0]
             self.put(self.ss, self.es, self.out_ann, [0, ['IR: ' + self.state]])
         elif self.state == 'BYPASS':