FD1771

WESTERN DIGITAl MOS/LSI FD1771 APPLICATION NOTE FLOPPY DISK CONTROLLER APPLICATION NOTE Introduction The FD 1771 is a MOS/LSI device that performs the function of interfacing a processor to a' flexible (Floppy) diskette drive. This single chip replaces nearly 80% of the required disk drive interface electronics. (See figure 1-1) .It provides tha data accessing controls and the bidirectional transfer of information between the processor's memory and the magnetically stored data on the diskette. The diskette data is stored in a data entry format compatible with the IBM 3740 specification (other formats may be used providing more data storage). In this format all information is recorded on tracks (radial paths) in sectors (arc sections) defined by a program.: rned heade'r asshown below: FLOPPY DISK FORMATTER/CONTROLlER Index Address Mark Data 1 1 1.1 1 1 0 0 oClock 1 1 0 1 1 1 1 ID Address Mark Data 1 1 1 1 1 1 '1 0 Clock 1 1 00 0 1 1 1 Data Address Mark Data 1 1 1 1 1 0 1 1 Clock 1 1 0 00 1 1 1 Deleted Data 1 1 1 1 1 00 0 Data Address Mark oClock 1 1 0 0 1 1 1 =FC =07 =FE =C7 =FB ==C7 =F8 =C7 These patterns are used as synchronization codes by the FD 1771 when reading data and are recorded by the formatting command, Write Track, when the FD 1771. is presented with data F7 through FE. Bytt' 1 6 "7 1-128 ,ITrack Byte> Sector ~ector Cyclic gap 2 Datd Data Data .gap 3 Nurntwr of Number U'flytn Hedundancy (17 Adcll"';S' CRe . (33 Bytes lero's (flO of Check ·(...