Fwd: Completed Floppy Disk Controller Design

From: Jeff Hellige <jhellige_at_earthlink.net>
Date: Wed May 16 04:50:48 2001

        For those interested in the SWTPc and SS-50 bus machines:

>Status: RO
>Sender: fufu-l_at_telia.com
>Reply-To: fufu-l_at_telia.com
>Date: Mon, 14 May 2001 08:47:25 -0700
>From: "Michael Holley" <holley_at_mail.hyperlynx.com>
>To: Multiple recipients of fufu-l <fufu-l_at_telia.com>
>Subject: Completed Floppy Disk Controller Design
>
>I have finished the design of a new floppy disk controller for the S30 I/O
>bus. The card emulates the SWTPC DC-4 with a few additions. The design uses
>a Western Digital WD2797 FDC that supports double density format. The WD2797
>is a superset of the WD1797 and WD1691 and is software compatible.
>
>The card will fit in an old 6800-style case or the newer 6809-style case
>with the connectors coming out the back. The clock frequency is programmable
>so the card should work with 3.5-inch drives.
>
>The design is complete but needs to be reviewed.(There are errors and
>omissions.) After a few weeks of review I will have 2 (or 4) boards made. I
>am looking for someone who has a system with SS30 I/O bus to help debug the
>board. After the design is tested I will order 10 or so boards with
>silk-screen and solder mask.
>
>The design documents can be found at:
>http://members.aol.com/swtpc6800/FDC2/FDC_Index.htm
>I still have some design documents in process and will add them when they
>are done.
>
>The difficulty I was having with a discrete logic design was board layout. I
>was going to use some 20-pin programmable logic devices such as the 16V8 but
>programming them is difficult. (I have an old Data I/O Model 29 programmer
>but I haven't turned it on in 10 years.) I was looking for an in-circuit
>programmable device.
>
>I decided to use the Xilinx XC9500 CPLD family. They are low cost ($6), the
>development software is free, and the programming hardware is simple.
>Another reason is that I have worked with these devices since they were
>developed by Plus Logic in the late 1980s. Somewhere I have a Plus Logic
>2020 engineering sample. The development software is based on the ABEL and
>Synario software that I developed at Data I/O.
>
>I chose the XC9572, which has 72 Macrocells and comes in an 84-pin PLCC
>package. This device holds all of the discrete logic devices needed in the
>design. The timer IC and one-shot IC are external along with the buffers. I
>could have connected the disk drive directly to the CPLD but I felt the low
>cost buffers would be easier to replace in the future. The device is
>re-programmable so design changes are easy. I am only using about half of
>the device now.
>
>For the PCB layout I went with ExpressPCB because they have free software
>and they do low cost double-sided boards. A friend of mine has had good luck
>with them. I have access to very high-end PCB layout software at work but I
>want the design to be public domain. (If I published the design files in
>PADS format you would have to buy a $10,000 PADS PowerPCB software package
>to modify them.)
>
>After the layout is done I will publish the PBC file. If someone wants to
>review the current design I can email you the file.
>
>The only rare part in the design is the WD2797; I bought 10 of them from BG
>Micro before I started the design. The rest of the parts are available from
>Digi-Key with exception of a few ICs that I found at Jameco. The complete
>kit of parts cost $50 plus about $40 for the circuit board. I am going to
>acquire enough parts to build 10 boards.
>
>I still need to write the calibration procedure and add the required test
>point to the board. I just noticed a trace clearance problem near pin one of
>the 34-pin connectors.
>
>The DDEN line is controlled by the CPLD so we can add the logic for MS-DOS
>floppies. This logic in not in the CPLD yet.
>-----------------------------------------------
>Michael Holley holley_at_hyperlynx.com
>Innoveda
>Phone: (425) 869-2320 Fax: (425) 881-1008
>Direct Line (425) 497-5075
>-----------------------------------------------
>--
>FLEX & UniFLEX Users' mailing List
>http://www.flexusergroup.com/
>http://w1.503.telia.com/~u50302970/
>
>

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Received on Wed May 16 2001 - 04:50:48 BST

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