Following is the documentation provided by Dysan Corporation for 
use with their Digital Diagnostic Diskette (DDD).
     Using the DDD, it is possible to align most floppy drives 
with no test equipment - other than your computer and a 
screwdriver or two.
     The program DDD.ASM is a generic one, and is useless until 
modified for a specific computer or controller board.  We will 
be maintaining copies of all of these "specific" versions on 
Technical CBBS ( (313) 846-6127 ), so if you modify this program 
for your own use, please pass a copy along to us there, so that 
others may also benefit from Dysan's contribution of this 
program to the public.
                         -Dave Hardy, CDP Corp., Technical CBBS

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       Requirements for using Dysan's Diagnostic Program


                        DYSAN CORPORATION
                           CE DIVISION

                    DRIVE DIAGNOSTIC PROGRAM
                           for CP/M-80

The Drive Diagnostic Program is a sample program showing how 
the Digital Diagnostic Diskette (DDD) can be used for Floppy 
Drive checking.

The program requires the following hardware to run:

     CRT with cursor positioning and clear screen commands.
     (The program is currently configured for a Hazeltine 1500.)

     CP/M-80 system with at least 32k of memory.

     At least one 8" or 5.25" floppy disk drive.

This source program is provided on an 8" single density, one-
sided diskette that is compatible with the CP/M-80 operating 
system.  The program provided will not run "as-is"; it must 
be modified by someone experienced in 8080 Assembly language, 
CP/M-80 and disk drive controller interfacing.

In order to make the program run with the target system, there 
are four assembly language subroutines that must be modified 
to interface with the system's disk controller/drive(s):

     1) "SELECT" - Selects and Homes the drive.
     2) "TRACK"  - Seeks to the track number found in register A.
     3) "HOME"   - Restores the selected drive's head to track 0.
     4) "READ"   - Reads sector in register "A" and exits with
                   error status.

The above routines must be coded within the Diagnostic Program, 
instead of calling the routines through the BIOS, because the 
BIOS may interfere with disk I/O operation (either by trapping 
disk errors or deblocking sector calls, i.e. where sector sizes 
are greater than 128 bytes).

The sample program was coded for use with the Western Digital 
FD-1793 floppy disk controller IC.  The program will work with 
other controllers (i.e. NEC uPD765 and Intel 8272 FDCs) by 
modifying the source program, as indicated above.  Because some 
disk controllers don't allow programmed access to the drive's 
INDEX signal (i.e. NEC and Intel), "Index Timing" and "Spindle 
Speed" testing are not possible with the current program.