* FDC9216
* SED9420C
Note: The CPC464, CPC472, 464 Plus and GX4000 are not equipped with a FDC chip.
== Accessing the FDC 765 ==
Usually single sided 40-track 3" disk drives are used in CPCs. For practical purposes, 42 tracks could be used — the limit is specific to the drive and some support more tracks but 42 is a good maximum. The FDC controller can be used to control 80-tracks and/or double sided drives, though AMSDOS doesn't support such formats. AMSDOS supports a maximum of two disk drives only.
== FDC Track Format ==
[[File:FDC765 Track Format.png]]
== Internal details of the chip ==
* [https://scarybeastsecurity.blogspot.com/2020/11/reverse-engineering-forgotten-1970s.html The decapped photos of Intel 8271, NEC D765 and Intel 8272 chips] prove that NEC D765 and Intel 8272 chips are identical.
* From [https://hackaday.com/2012/08/13/taking-a-look-at-decapped-ics/#comment-734991 a comment in the hackaday website]: "Internally this is a microcoded part with a primative controller of NEC’s own design. Testing microcode embedded in a part can be troublesome. The uPD765 had a few extra gates associated with the DMA Request and DMA Ack pins. Presenting a certain illegal combination here places the part into a “test” mode and allows the sequencer microcode to be output on the normal Data pins. The sequencer microcode is responsible for high level commands such as Read Track, Recalibrate, Format Track, or Write Data. There is a similar test mode for the nano-code array which serializes data at the floppy disk head."
== FDC Block Diagram ==
[[File:FDC Intel 8272A block diagram.gif]]
== Generic System Diagram ==
The Amstrad CPC and Amstrad Plus do not have a DMA controller associated with the FDC. The INT pin of the FDC is not connected either.
[[File:UPD765A System Diagram.png]]
== 3-inch Floppy Drive Interface ==
[[File:Interface FDC - Floppy drive.png]]
== FDD Block Diagram ==
[[File:Floppy Disk Drive - Block Diagram.png]]
== Datasheets ==
* [[Media:UPD765_App_Note_Mar79.pdf| NEC uPD765 Datasheet preliminary (1979)]] [[Media:UPD765 Datasheet OCRedD765 NEC.pdf]] [[Media:UPD765-NEC.pdf]] [[Media:Z765A datasheet.pdf]] - uPD765 disc controller* [https[Media://www.threedee.com/jcm/terak/docs/Intel%208272A%20Floppy%20Controller.pdf Intel 8272A Datasheet preliminary (1982).pdf]] [[Media:Datasheet.hk_d8272a_2873060.pdf|Intel 8272A Datasheet (1986)]] - Identical Licensed clone of the uPD765. * [https[Media://scarybeastsecurityFDC9229BT Datasheet.blogspot.com/2020/11/reverse-engineering-forgotten-1970s.html The decapped photos of both chipspdf] prove they are identical] - FDC9229BT data separator* [[Media:FDC9229BT DatasheetSED9420.pdf]] - FDC9229BT SED9420C data separator (that usually assists the uPD765 chip)
* [[Media:DDI Schematic.png]] - DDI-1 Schematic (disc interface for CPC464)
* [[Media:Panasonic-3 inch Floppy Drive EME-150.pdf]] Panasonic EME-150M 3inch Floppy Disk Drive Datasheet* [[Media:NEC_FD1035_Floppy.pdf]] - NEC FD1035 3.5inch Floppy Disk Drive Datasheet (1984)
== External links ==
*[http://quasar.cpcscene.net/doku.php?id=assem:fdc Quasar FDC documentation (in french)]
*[https://64nops.wordpress.com/2021/07/04/a-la-decouverte-du-fdc/ FDC blog articles (in french)]
*[https://info-coach.fr/atari/hardware/FD-Hard.php Atari ST Floppy Disk hardware analysis]
[[Category:CPC Internal Components]][[Category:Programming]][[Category:DATA Storage]][[Category:Electronic Component]]