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+arch/z80/src/z180
+^^^^^^^^^^^^^^^^^
+
+The arch/z80 directories contain files to support a variety of 8-bit architectures
+from ZiLOG (and spin-architectures such as the Rabbit2000).  The arch/z80/src/z180
+sub-directory contains logic unique to the classic Z180 family of chips.
+
+Files in this directory include:
+
+z180_head.asm
+	This is the main entry point into the Z180 program.  This includes the
+	handler for the RESET, power-up interrupt vector and address zero and all
+	RST interrupts.
+
+z180_rom.asm
+	Some architectures may have ROM located at address zero.  In this case, a
+	special version of the "head" logic must be used.  This special "head"
+	file is probably board-specific and, hence, belongs in the board-specific
+	configs/<board-name>/src directory.  This file may, however, be used as
+	a model for such a board-specific file.
+
+	z180_rom.S is enabled by specifying CONFIG_LINKER_ROM_AT_0000 in the
+	configuration file.
+
+	A board specific version in the configs/<board-name>/src directory can be
+	used by:
+	
+	1. Define CONFIG_ARCH_HAVEHEAD
+	2. Add the board-specific head file, say <filename>.asm, to
+	   configs/<board-name>/src
+	3. Add a file called Make.defs in the configs/<board-name>/src directory
+	   containing the line:  HEAD_ASRC = <file-name>.asm
+
+Make.defs
+	This is the standard makefile fragment that must be provided in all
+	chip directories.  This fragment identifies the chip-specific file to
+	be used in building libarch.
+
+chip.h
+	This is the standard header file that must be provided in all chip
+	directories.
+
+z180_initialstate.c, z180_copystate.c,  z180_restoreusercontext.asm, and
+z180_saveusercontext.asm, switch
+ 	These files implement the Z180 context switching logic
+
+z180_schedulesigaction.c and  z180_sigdeliver.c
+	These files implement Z180 signal handling.
+