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uPD372_Floppy_Disk_Controller_Mar77


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N'ECm                        Inc.                                                         J.LPD372




                      FLOPPY DISK CONTROLLER
                                       USERS' MANUAL




Five Militia Drive/Lexington, Massachusetts 02173           Telephone (617) 862-6410   Telex 92-3434
                                                    Rev/2
  NEC MICROCOMPUTERS, INC.

            uPD372D

LSI FLOPPY DISK CONTROLLER CHIP

         USERS' MANUAL




                             March 11, 1977
     The NEC uPD372D is a high performance N-channel LSI floppy
disk controller designed to- interface between most minicomputers
or microprocessors and most floppy disk drives.
     The uPD372D is the most versatile floppy disk controller
chip available.
FEATURES - Compatible with IBM3740 format
         - Compatible with Shugart Minifloppy format
         - Compatible with many other formats
         - Generates and checks Cyclic Redundancy Characters
         - Initiates operations at address marks
           or physical index
         - Formats clear disks
         - Handles up to four floppy disk drives
         - Can read or write on one drive while simultaneously
           track seeking on another
         - Track stepping rate and step pulse width
           are programmable
         - Sector size programmable from one byte
           to one sector per track
         - Data transfer rate easily changed
         - Standard power supply voltages +12V, +5V, -5V
     The uPD372D is compatible with most floppy disk drives
including:
         Calcomp 140             Pertec FD400
         CDC BR803               Potter DD4740
         GSI 050                 Remex RFS7400
         GSI 110                 Shugart SA400
         Innovex 210             Shugart SA900
         Orbis 74                Sycor 145
         Persci 75




                                       2
         TABLE OF CONTENTS


INTRODUCTION                      4

INPUT/OUTPUT SIGNALS              6

     INTRODUCTION                 6

     PROCESSOR INTERFACE          6

     DISK DRIVE INTERFACE         9

ADDRESSABLE INTERNAL REGISTERS   12
     INTRODUCTION                12
     WRITE REGISTERS             14
     READ REGISTERS              22
DATA CONDITIONER                 26

     INTRODUCTION                26

     DATA CONDITIONER EXAMPLE    30

FLOPPY DISK CONTROLLER EXAMPLE   32

     HARDWARE                    32

     SOFTWARE                    35

uPD372 SPECIFICATIONS            65




                    3
                     INTRODUCTION


     The uPD372 may be interfaced directly to a host processor as
shown in Figure 1 or it may be interfaced to a controller
processor which in turn is interfaced to the host processor as
shown in Figure 2. Most processors interfaced to the uPD372
must, when reading from or writing a record on the disk, be
completely dedicated to the task of controlling the disk
drive(s). These periods may last several milliseconds.    If the
nature of the other tasks performed by the host processor allows
them to be neglected for this length of time, then the uPD372 may
be interfaced directly to the host processor. Otherwise, a
controller processor is required.

     Whichever approach is chosen, the floppy disk drive control
workload is shared between the uPD372 hardware and the
processor(s) software.

     The uPD372 converts information, which the software
transmits to uPD372 internal registers, into commands and serial
data which are transmitted to the disk drive(s). The uPD372
converts status signals and serial data from the drives into
register information which is read by the software. The uPD372
also controls the timing of most disk operations and performs
many other tasks such as Cyclic Redundancy Character generation
and checking.

     The software tasks are usually divided into two groups as
shown in Figures 1 and 2. The Drive Handling Routines control
sector reading and writing and track seeking. The Floppy Disk
Operating System contains the executive programs which instruct
the Drive Handling Routines to read or write a particular sector
on a particular track. The Floppy Disk Operating System
programs also decide from what area of memory write data should
be taken and into what area of memory read data should be stored.

     A uPD372 interface between a uPD8080A microprocessor and an
IBM3740 compatible drive is shown in the right hand side of
Figure 10 in the FLOPPY DISK CONTROLLER EXAMPLE section. This
circuit may be interfaced directly to a uPD8080A host processor
or to a uPD8080A controller processor similar to the example
shown in the left hand side of Figure 10.

     Since the disk drive(s) operate under program control,
complete uPD8080A assembly listings of the Drive Handling
Routines with extensive comments are included in the FLOPPY DISK
CONTROLLER EXAMPLE section. The listings describe the sequence
of events of each disk operation. Although the sequences are
specific to IBM3740 format and to a uPD8080A microprocessor,
sequences for other formats are very similar in most respects and
the uPD8080A instructions used are largely limited to simple
INPUTS, OUTPUTS, CONDITIONAL JUMPS, etc., which are similar to
those of other processors.



                                    4
                                                                                                           FLOPPY DISK
                                                                                                             DRIVE(S)
                                          I                          uPD372
                                                                                                       I
                                          I                                   r---    DRIVERS          



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