- Introduction
AFR is a project (program + schematic circuit) to connect Amiga external floppy to the PC parallel port and to create a .adf image for the great UAE emulator (thanks to all the people working around it). All you need is a PC with a BIDIRECTIONAL parallel port and some time to build the circuit. Note: on new mother board LPT can be configured as SPP, ECP and EPP. If the program is not able to read data at all, try changing this parameter in your machine bios setup. (On my machine AFR works only with SPP and EPP, but not with ECP). Moreover be aware of USB host controller: on some machine (like mine) it conflicts with the LPT port, so you have to disable it. I would be pleased to know if someone else build this circuit and to know how it works (my prototype is working quite fine). Obviously Amiga custom circuit are more flexible with old and almost rotten disks (some kind of real oversampling PLL is used inside of them), but even with my circuit you should be able to read almost all of your old disks. Some note about disk import speed:
P200 MMX Intel : 46 sec.
P100 Cyrix (no ext. cache) : 82 !!!!
For any question or suggestion please contact me by e-mail!
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- AFR Usage
The program is really very simple and little words are needed to get it working. When the program starts it asks you about your LPT port address. Once selected you enter the main program mask. Here all you have to do is to insert the name of the disk image you are going to read in, then the floppy will start reading. If you don't want to read any more disk just press enter when you are asked about the file name. While the program is reading a disk you can press ESC key to get back to the filename mask. Please do not blame me for not having included a user interface but I spend all the time I had (August 1997) to develope the circuit and to write MFM decoding code (it was not quite simple because of the lack of infos about some technical questions).
- Copyright
(C) 1997, Marco Veneri
Really simple: I do not want to make money with this project but, obviously, no one else must ! I put all the stuff in the public domain because I think that someone could be interested in the code or in the schematic. Moreover if someone will make some upgrade or modify to my source or schematic I hope he will let me know something about it. I also hope that if someone makes any further version or project based on my AFR he will report at least a greeting to me ! Finally, if someone makes money with AFR and start living at Honolulu..... Fuck off!!
- The Circuit
The circuit is made with 5 generic low-cost ICs and, once built, needs only to be trimmed for optimal performance.Note: trimmer R4 must be a multiturn! The ICs are:
1 - TLC555 : every ones knows this IC but be carefull: in my circuit it is used in an original way, infact it emulates a really stupid 'PLL' ( this is not quite exact ). It is the heart of the circuit since it must recover the bit clock of the data stream flowing out of the drive. This IC can NOT be replaced with a normal (non CMOS) 555.Also TS555 is working fine. I've no infos about 7555 up to now.
2 - 74LS374: this is an 8-bit buffer used to latch data. With only a little effort this IC could probably be eliminated at all.If someone make such a modify please let me know !
3 - CD4040 : It is used to generate two clocks: the first is the latch pulse for the 374 and the clear pulse for the shift register. The second clock is a trigger signal for the PC LPT and is polled by the software to read byte.
4 - 74LS14 : some inverters. Two of them are used to extract the front edge from the incoming bitstream. This pulse is used to reset the oscillator.
5 - 74LS164: shift register
Once you have biult your board you must make just one operation. Connect all up, insert a disk (Amiga format) and launch the AFR program. Start reading the disk image. Rotate the multiturn trimmer for faster and best disk reading. You can use the SECTOR-METER to find the optimal position. All the circuit needs an external power supply with +5 and +12. A small PC power supply would be quite good!
- PCB Notes
The PCB layout I've included in this version of AFR is a single face PCB, so anyone could make it with just a little effort. On the component side of the PCB you must also put some 'bridge' useing some short stub of wire (see top.bmp file).In the lower-left side of the PCB you'll find the 4 pads to connect the external power supply (2 grounds, +12 and +5). In the middle there is the P2 connector: use this holes to wire the DB23 female floppy connector (to do this you must use 12 short stubs of wire). On the right side is P1 connector. Again use short stubs of wire to connect the DB25 male PARALLEL connector.
- TODO
I collected some suggestion and hint for future expansion of AFR porject. I don't know if I'll have time to implement them, anyway here they are:
- Win 95 GUI
- Connecting a normal 1.44 PC floppy disk.
- Attention
I assume no responsibility for the consequences of use of such program and circuit, nor for any problem or hardware damage which may result from its use.
- Test suggestion
Here are some tests to do after you have build your AFR circuit:
- Before connecting AFR circuit to PC or floppy or to the power supply check the following connections:
- pin 23 of DB23 connector should be connected to +12V supply
- pin 12 of the DB23 connector should be connected to +5V supply
- pin 15 of DB23 connector should be connected to pin 12 of the DB25 connector
- pin 3, 4, 5, 6, 7 of DB23 connector should be connected to power GND
- pin 19, 20, 21, 22, 23, 24, 25 of DB25 connector should be connected to power GND
If this is all OK then you can proceed useing the AFR circuit.
- E-Mail
For feedback about AFR contact marco_veneri@hotmail.com
For feedback about this webpage contact metamonk@yahoo.com
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