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+This is a test release of the ZPU.
+ZPU is a 32 bits stack CPU. This package contains a VHDL implementation
+suitable for FPGAs. It was tested using a Xilinx Spartan 3 1500 FPGA.
+
+The author of the ZPU is Øyvind Harboe (oyvind.harboe zylin.com) and the
+license is the BSD one. Portions of this package were developed by Salvador E.
+Tropea (salvador inti.gob.ar) and others. Some portions are under the GPL
+license.
+
+Øyvind also added a ZPU target to the gcc/gdb.
+
+For more information about the ZPU core please visit:
+http://www.zylin.com/zpu.htm
+http://www.opencores.org/projects.cgi/web/zpu/overview
+
+What are the files?
+-------------------
+
+zpu_medium.vhdl
+ZPU CPU, medium version.
+
+zpu_small.vhdl
+ZPU CPU, small version (Dual Port RAM only!).
+
+zpu_pkg.vhdl
+Package containing the declarations for the ZPU library.
+
+devices/phi_io.vhdl
+The very basic I/O peripherals needed for the standard C library. It includes a
+timer (64 bits clock counter) and an UART (8N1 without FIFO).
+This is known as the PHI I/O layout, this implementation isn't complete. Only
+the above mentioned peripherals are available.
+
+devices/timer.vhdl
+64 bits clock counter maped by the PHI I/O.
+
+devices/trace.vhdl
+This is used for debug purposes. The ZPU have a debug port to connect this
+module. It can generate an execution trace log during the simulation.
+
+devices/txt_util.vhdl
+Useful text handling routines for the simulation.
+
+devices/br_gen.vhdl
+Fixed baud rate generator for the UART.
+
+devices/rx_unit.vhdl
+UART Rx module.
+
+devices/tx_unit.vhdl
+UART Tx module.
+
+roms/rom_pkg.vhdl
+Package containing the declarations for the memories used by the small and
+medium ZPU.
+
+roms/dmips_bram.vhdl
+A memory that maps to Xilinx BRAMs and contains the Dhrystone Benchmark,
+Version 2.1 (Language: C). This memory can be connected to the ZPU for
+simulation or hardware implementations. The code assumes a 50 MHz clock to
+compute the benchmark. The minimum size for this block should be 32 kB.
+
+roms/dmips_dbram.vhdl
+Same as roms/dmips_bram.vhdl, but dual ported. Suitable for the small ZPU.
+
+roms/hello_bram.vhdl
+A memory that maps to Xilinx BRAMs and contains a simple "Hello World!"
+program (C compiled). This memory can be connected to the ZPU for
+simulation or hardware implementations. The minimum size for this block
+should be 16 kB.
+
+roms/hello_dbram.vhdl
+Same as roms/hello_bram.vhdl, but dual ported. Suitable for the small ZPU.
+helpers/zpu_med1.vhdl
+This is a helper that connects a ZPU to its memory and the PHI I/O space.
+
+testbenches/dmips_med1_tb.vhdl
+A simple testbench to simulate the medium ZPU (behavior).
+
+testbenches/small1_tb.vhdl
+A simple testbench to simulate the small ZPU (behavior).
+
+fpga/dmips_med1.vhdl
+A wrapper to implement the medium ZPU in an FPGA. This example was designed
+for a GR-XC3S board from Pender, but should be easily adapted to other
+boards.
+
+fpga/hello_med1.vhdl
+Same as fpga/dmips_med1.vhdl, but uses less memory, enough for the "Hello
+Wold!" test.
+
+fpga/dmips_small1.vhdl
+Same as fpga/dmips_med1.vhdl, but for the small ZPU.
+
+fpga/hello_small1.vhdl
+Same as fpga/hello_med1.vhdl, but for the small ZPU.
+
+
+ZPU library?
+------------
+
+The following files are part of a library I called ZPU:
+
+zpu_pkg.vhdl, zpu_medium.vhdl, zpu_small.vhdl, txt_util.vhdl, timer.vhdl,
+rx_unit.vhdl, tx_unit.vhdl, br_gen.vhdl, phi_io.vhdl and trace.vhdl.
+
+You should group them inside a library called zpu. This procedure is
+tool-chain dependent. In the ISE tool you must add a library and them move
+these files to the library.
+
+If you don't know how to do it with your tools you can just replace all the:
+
+library zpu;
+use zpu.xxxxxx.all;
+
+code by:
+
+library work;
+use work.xxxxxx.all;
+
+
+Which files are needed for simulation?
+--------------------------------------
+
+You need all the files that compose the zpu library plus:
+1) A memory containing a program, i.e.:
+roms/rom_pkg.vhdl and roms/dmips_bram.vhdl
+2) A testbench (including the memory and I/O interconnections):
+aux/zpu_med1.vhdl and testbenches/dmips_med1_tb.vhdl
+3) Be careful to include only the medium or the small ZPU. Also note that
+the small uses dual port BRAMs, i.e. roms/dmips_dbram.vhdl The testbench
+for the small ZPU is small1_tb.vhdl
+
+
+Which files are needed for synthesis?
+-------------------------------------
+
+This is similar to simulation, but:
+1) You should avoid trace.vhdl.
+2) The top level should connect to the FPGA pins, replace dmips_med1_tb.vhdl
+by fpga/dmips_med1.vhdl or fpga/hello_med1.vhdl
+
+
+What resources are needed in the FPGA?
+--------------------------------------
+
+The DMIPS benchmarks needs aprox (Xilinx Spartan 3):
+
+Medium ZPU:
+
+Flip Flops:   498
+LUTs:        1877
+Slices:      1032
+BRAMs:         16
+Multipliers:    3
+
+The hello world example needs less memory:
+
+Flip Flops:   496
+LUTs:        1871
+Slices:      1027
+BRAMs:          8
+Multipliers:    3
+
+
+Small ZPU:
+
+Flip Flops:   373
+LUTs:         706
+Slices:       434
+BRAMs:         16
+
+The hello world example needs less memory:
+
+Flip Flops:   371
+LUTs:         701
+Slices:       431
+BRAMs:          8
+
+
+The board should contain an RS-232 transceiver. A push button (active when
+pressed) is also used, for reset.
+
+
+Ok, I synthetized it and put in the FPGA, what now?
+---------------------------------------------------
+
+Connect the RS-232 board output to a terminal (a PC). Setup the terminal for
+115200 8N1 reception and press the reset push button. You should get the
+program output. You can change the baudrate in the toplevel VHDL.
+
+
+Please tell me if you succeed or failed!
+Enjoy, Salvador E. Tropea
+