Search

To successfully accomplish a bit synchronization, a synchronizer should exploit a preamble pattern. A MFM (modified frequency modulation) flag is uses as a preamble in a PJM (phase jitter modulation) mode RFID standard. In the recent work, a synchronizer for a PJM mode tag was proposed, which is composed of several correlators. In this paper, we present a new bit synchronizer in which a coarse synchronization is done as in the previous work while a fine synchronization is performed via exploiting a violation bit included in the MFM flag. We show that the proposed synchronizer can significantly reduce the overall hardware complexity at the expense of slight burden to a demodulator structure. Through simulation, we also show that its performance is comparable to that of the previous system despite its hardware simplicity.

We will report on a magnetic head positioning control system and a track following control method through which increased capacity and high speed has been achieved and in which a 3.5 inch 16 MB high density flexible disk drives (FDD) is employed.

The 5-1/4" floppy disk drive was introduced in 1976 as a low cost alternative to the 8" IBM standard flexible disk drive. Originally aimed at the blossoming small business and personal computer industry, these small, low-cost drives offered a maximum unformatted data capacity of only 110 kbytes. Although the 5-1/4" floppy is now 2 years old, most drives being shipped by the handfull of 5-1/4" floppy manufacturers is still capable of only 110 kbytes of storage. Because of the popularity of the 5-1/4" floppy and increased demand for storage by the suppliers of microcomputer systems, most of these manufacturers are now trying to increase the capacity of their drives by in creasing bit density (using MFM or M2FM recording techniques) and/or using double sided heads. One manufacturer, however, Micropolis Corporation, Canoga Park, California, has been offering a drive since the spring of 1977 which provide 4.4 times the normal density on a single side of a standard 5-1/4" diskette. First available only in disk memory subsystems, Micropolis' 480 kbyte unformatted capacity drive is now supplied, on an OEM basis, to many microcomputer system manufacturers. Originally viewed as a novelty, the drive is now widely accepted as a highly reliable alternative to other low capacity 5-1/4" drives. Micropolis expects to ship nearly 20,000 drives over the next year. The double-sided Micropolis drive now being supplied in evaluation quantities is capable of I megabyte of storage per drive! How has Micropolis been able to offer so much more capacity? The drive mechanism incorporated two technologies already well-proven in the peripheral industry yet not then introduced to 5-1/4" floppy design: Increased Bit Density ------ MFM Data Recording Increased Track Density ---- 100 Tracks per inch (77 tracks total) MFM (Modified Frequency Modulation) increases the nominal capacity of 110 kbytes to 220 kbytes. The increase from 35 tracks to 77 tracks yields 77/35 X 220 = 480 kbytes.

Faster devices have largely superseded floppy disks but there is still a demand for their use. PCs without floppy drives are still not common except in corporate networks. Most if not all floppy disks are now the 1.44 MB format 3.25” disks. This chapter introduces the most commonly used floppy disk formats and the structure of boot records and file allocation tables (FAT). It also describes the floppy disk interface and the functions of the PC's floppy disk controller (FDC). Floppy disks can be formatted as “bootable” or data only. The boot record contains a number of useful parameters and may contain code that will load and run. Bootable disks must also contain two other programs: IBMIO.COM and IBMDOS.COM (or IO.SYS and MSDOS.SYS). These, in turn, are responsible for locating, loading, and running the command interpreter. Fault diagnosis within floppy disk drives should only be carried out when one is certain that the disk interface and controller can be absolved from blame. Thus, whenever the drive in a single-drive system is suspect, it should first be replaced by a unit that is known to be good.

A self-consistent magnetic recording modeling method is presented which has proven useful in recording channel design on thin media. Improvements in the magnetic model and in the mathematical treatment stabilize the iterative process and reduce computer storage requirements. Major and minor media loops are fitted to quickly computable bipolynomials. Mathematical improvements include using a strong band diagonal demagnetization matrix, analytic integration with quadratic magnetization fitting, and Newton-Raphson iteration, which gives rapid convergence without underrelaxation. Quantitative predictions of timing errors in 16-bit modified frequency modulation (MFM) data patterns on a 350-bit/mm, 20-track/mm disk memory are presented, as well as playback amplitudes and saturation currents. Predictions can also be compared with experimental read/write data to determine system parameters. Two examples are given: the inference of the head efficiency and of the effective high-frequency medium squareness.

This paper describes the development of a 3.5 inch floppy disk system. (Unformatted capacity : 437.5 K bytes/surface, Linear recording density :7610 bpi, Track density : 135 tpi) This system employs several new technologies. (1) Material with high coercive force. (2) Metal hub for precise disk centering. (3) Narrow width track head for read and write. (4) Medium Chucking mechanism. (5) Hard case for medium protection.

A magnetic tape data storage system called the High Capacity Mini-Recorder has been designed and is in manufacture for Bell System applications. It can be operated in either the streaming or the incremental (start/stop) mode. It uses the recently available DC600 1/4 inch, 600 foot, high density tape cartridge manufactured by 3M Corp. Data are written in blocks of 2K bytes on five serpentine tracks at a linear density of 10,000 flux transitions/in. (ftpi) using Modified Frequency Modulation (MFM) encoding. The total user capacity is 26 Mbytes. The addition of a binary head positioning mechanism increases the number of tracks to 10 and the capacity to 52 Mbytes. Burst error correction capability up to several thousand bits is provided by an Interlaced Sum-set code. Tape speed for read or write is 50 inches/sec. (ips), and for search is 100 inches/sec. The average data rate is 37 Kbytes/sec. for streaming. The data electronics incorporates write precompensation for peak shift and provides data recovery using phase-locked loop decoding techniques. A controller based on an 8086 microprocessor with an 8 MHz clock allows the system to be operated using a high level command set.

A bipolar technology floppy disk controller using LS, I2L and analog circuitry will be discussed, citing system level advantages such as an on chip PLL.

This report will cover the use of one CMOS and two bipolar ICs to provide analog and digital signal processing for 25Mb/s Winchester disk drives. A single chip 25Mb/s data separator-encoder realizes both modified frequency modulation and