Floppy Disk Emulation Explained by Example

By Alex Lukacz

Apple II Mass Storage Devices• Disk II Port - Disk II protocol• Semi-Virtual Diskette (SVD) http://www.thesvd.com/• bootZero http://www.bootzero.com/HDDD_A2_v1.2/HDDD_A2v1.2.html• SDISK II - DISK II emulator for APPLE II http://tulip-house.ddo.jp/digital/SDISK2/english.html• http://tulip-house.ddo.jp/digital/SDISK2V1/english.html• USB AII-SPI-DSK http://maclcd.blogspot.com.au/search/label/Disk%20%5D%5B• CHED http://lukazi.blogspot.com.au/search?q=ched

• Disk II Port - Smartport protocol• Apple //c Smartport Compact Flash Adapter http://www.users.on.net/~rjustice/SmartportCFA/SmartportCFA.htm• Smartport Virtual Hard Drive (SPVHD) http://www.spvhd.org/

• Apple II Slot - Floppy Drive (Replaces the floppy drive controller as well as the drive unit)• Double Action Pseudo Disk / PseudoDisk2 http://alexfreed.com/FPGApple/pseudodisk.html• http://www.applelogic.org/PseudoDisk2.html• iDisk https://sites.google.com/site/idiskapple2/home

• Apple II Slot - Hard Disk Drive (Replaces the floppy drive controller as well as the drive unit)• Apple II IDE/ATA interface http://s.guillard.free.fr/Apple2IDE/Apple2IDE.htm• CFFA / CFFA3000 (inludes floppy emulation) http://dreher.net/?s=projects/CFforAppleII&c=projects/CFforAppleII/main.php• Microdrive IDE controller http://www.reactivemicro.com/• Focus IDE HD Controller http://16sector.com/

• Serial port• Apple Disk Transfer ProDOS (ADTPro) http://adtpro.sourceforge.net/• Pocket Serial Host http://osgeld.a2hq.com/category/projects/pocket-serial-host/

• Speaker port• Online Apple II Disk Server http://asciiexpress.net/diskserver/• Cassette tapes using a music payer (PC/iPad etc). Source data from Brutal Deluxe Software http://www.brutaldeluxe.fr/projects/cassettes/index.html

• Joystick Port• Apple //t http://atomsandelectrons.com/blog/2010/04/apple-t/

Three generations of Apple II floppy disk drives.

• 1. 5.25 inch floppy disk.• 2. Smartport.• 3. 3.5 inch floppy disk.

• Apple II Models and the generation disk technology they support :-• II 1• II+ 1• IIe 1• IIc 1• IIe with Liron or Superdrive card 1, 2• IIc with ROM 0 or later 1, 2• IIGS 1, 2, 3• IIc+ 1, 2, 3

Fundamentals

Bitstream

• Sync Bytes – 10bits 1111111100 – 4 in a row.

11111111, 00111111, 11001111, 11110011, 11111100

• Encoding – 1 bit must be high, only 1 pair of consecutive zero bits. 256 bytes of data translates to 342 bytes.

• Counters to keep track of Tracks and Sectors.

Track Structure

Emulation

CHED (Combined Hardware Emulated Drives)

Timing

Debugging (Signals)

Debugging (Data)

CHED2?

Reference

• Disk II• Chapter 9 of "Understanding the Apple IIe" by Jim Sather• Chapter 3 of "Beneath Apple DOS (Fifth Printing)" by Don Worth and Pieter Lechner

• Smartport• Apple IIGS Firmware Reference ISBN 0-201-17744-7 – Chapter 7• Apple IIc Technical Reference Manual ISBN 0-201-17752-8 – Appendix I Firmware

listings – Protocol Converter• Apple Smartport technical note – smartport packet• Inside the Apple II - Chapter 9• Beneath Apple Dos

Smartport and 3.5 inch Drive Support

• Smartport uses packets and WRPROT line for ACK, PH0 for REQ hand shaking.

• 3.5 inch Drive ?

Thanks. Hack away and have fun.