zxuno-git/cores/VIC20

--- VIC-20 port for ZX-UNO and modifications by Quest 2016
--- Added 16K expansion (selectable by keyboard), 3 embeded cartridges, cassete load via audio, 
--- vga switch by keyboard, PAl Kernal and timings.
---
---
--- Original core by MikeJ 
---


README ORIGINAL:
------------------

--
-- A simulation model of VIC20 hardware
-- Copyright (c) MikeJ - Jan 2008
--
-- All rights reserved
--
-- Redistribution and use in source and synthezised forms, with or without
-- modification, are permitted provided that the following conditions are met:
--
-- Redistributions of source code must retain the above copyright notice,
-- this list of conditions and the following disclaimer.
--
-- Redistributions in synthesized form must reproduce the above copyright
-- notice, this list of conditions and the following disclaimer in the
-- documentation and/or other materials provided with the distribution.
--
-- Neither the name of the author nor the names of other contributors may
-- be used to endorse or promote products derived from this software without
-- specific prior written permission.
--
-- THIS CODE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
-- AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
-- THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
-- PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE
-- LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
-- CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
-- SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
-- INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
-- CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
-- ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
-- POSSIBILITY OF SUCH DAMAGE.
--
-- You are responsible for any legal issues arising from your use of this code.
--
-- The latest version of this file can be found at: www.fpgaarcade.com
--
-- Email vic20@fpgaarcade.com
--

-- Revision list

-- version 002 Spartan3e release (minor bug fixes)
-- version 001 initial release

********************************************************************************
     Note :

     Switch0 is used to switch between PAL and VGA (31K). Up (on) is VGA
     and LED0 will come on.

     Switch1 when up (on) will ENABLE the external flash memory - plugging in
     the cartridge.

     Switch3 and 2 are a two bit bank select.

     The push button on the rotary control is used for reset.
********************************************************************************
Note : The ROM images in this distribution are BLANK and must be replaced.
********************************************************************************

 This is the original Commodore VIC-20 home computer recreated in VHDL.

 The following scripts will create a directory called 'build', copy the source
 files, run the sythesizer and Xilinx place and route tools.

 Assuming the Xilinx tools are installed and working, expand the distribution
 zip file (maintaining directory structure).

 Fire up a command prompt and navigate to the directory.

 run :

 Build_roms.bat - this will convert the files in the Roms directory to VHDL
		  files (also in the Roms directory). These may then be used
		  if you wish to simulate the design.
		  ( Note - the rom binaries provided are blank. )


 then either :


 Build_xst.bat - Xilinx build script using Xilinx XST
		 (uses vic20_xst.ucf constraints file)

 if you add a /xil switch, the script will not run the synthesizer, just the
 place and route tools. You will be left with a .bit file in the Build directory
 you can use to program a chip. Remember to modify the .ucf file for your
 pinout.


 Additional Notes


Audio out :

   This DAC requires an external RC low-pass filter:

   audio_o 0---XXXXX---+---0 analog audio
		3k3    |
		      === 4n7
		       |
		      GND


 Video Out :

   Video out DAC's. Values here give 0.7 Volt peek video output.

   Use the following resistors for Video DACs :

   video_out(3) 510
   video_out(2) 1k
   video_out(1) 2k2
   video_out(0) 4k7

********************************************************************************
  H O W   T O   P R O G R A M   T H E   F L A S H
********************************************************************************

The Vic20 FPGA uses the onboard Intel Strata flash to store cartridges.
Each cart is allocated 8K (0x0000 - 0x1FFF)

Switch1 when on (up) ENABLED the cartridge.

Bits 14 and 13 are wired up to switches 3 and 2 on the board so ->

Switch  Flash address mapped into Card space (0xA000 - 0xBFFF in VIC20 address map)
3   2

off off 0x0000 - 0x1FFF
off on  0x2000 - 0x3FFF
on  off 0x4000 - 0x5FFF
on  on  0x6000 - 0x7FFF

letting you can have four cartridges accessable at the same time.

First, you must convert the binary cart file into an MCS file.

I use srec_cat.exe (SRecord) to do the conversion : http://srecord.sourceforge.net/
I just downloaded the Windows executable.

To convert Jupiter Lander for example :

srec_cat Jupiter_Lander.prg -binary -exclude 0x0000 0x0002 -offset -0x0002 -o lander.mcs -intel

where offset is the Flash base address above (plus 2).
Note that PRG files have an additional 2 bytes added at the start which must be
stripped off to get an original ROM image. This is what the -exclude does.

To program the flash you can use the very nice PicoBlaze RS-232 StrataFlash
programmer by the great Ken Chapman.

http://www.xilinx.com/products/boards/s3estarter/reference_designs.htm

It comes with good instructions, but you basically connect an RS-232 cable from the
Spartan3e starter kit board to your pc, download the PicoBlaze programmer bit file
using impact, fire up Hyperterminal, E to Erase all then P to program. Send the
MCS file using the Send Text File option in Hyperterminal. When complete, download
the vic20.bit design and play!

The PicoBlaze design from Xilinx uses the female RS-232 connector on the Starter kit
board. I have modified it to use the male connector, then you can use a standard
female-to-female null modem cable with a pin 2-3 swap. This bit file is on the resources
page for download.

 Cheers,

 MikeJ