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+pjrc-8051 README
+^^^^^^^^^^^^^^^^
+
+This port uses the PJRC 87C52 development system and the SDCC toolchain.
+
+The PJRC 87C52 development system can be obtained from http://www.pjrc.com/.
+
+The SDCC toolchain is available from http://sdcc.sourceforge.net/.  All
+testing has been performed using verison 2.6.0 of the SDDC toolchain.
+
+Building the SDCC toolchain
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The SDCC toolchain is built with the standard configure/make/make install
+sequence.  However, some special actions are required to generate libraries
+compatible with this build.  First start with the usual steps
+
+  download
+  unpack
+  cd sdcc
+  ./configure
+  make
+
+But before installing, we need to apply a patch to the SDCC 2.6.0 source.
+WARNING:  This patch is specific to the particular combination of CFLAGS
+that are used in the compilation.  If you change Make.defs, then you will
+likely have to change the patch as well.
+
+  Apply sdcc-2.6.0.patch
+  cd sdcc/device/lib
+  make model-mcs51-stack-auto
+
+Then
+
+  cd sdcc
+  make install
+
+Status
+^^^^^^
+
+On December 9, 2012, I made updates so that the 8051 port could use the
+newest SDCC toolchain (a pre-3.2.1 at that time).  However, when I attempted
+to build the PJRC-8051 configuration, I got type incompatibility errors
+from sched/os_bringup.c.  From what I gather by googling, this is a compiler
+bug related to the --stack-auto option.
+
+I have not been successful working around those bugs and I believe that
+these are 8051-related bugs in the SDCC toolchain.  This needs to be
+revisited with a later version of SDCC.
+
+This configuration was last successfully built and tested with a ca.
+2.6.0 SDCC release.  Support for that older toolchain was removed in
+NuttX revision -r5423.  If you wanted to used those older toolchains,
+you would need to revert to a pre-r5423 revision.