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Article #75 (75 is last):
From: JTKirk  (by way of Michael Current)
Newsgroups: freenet.sci.comp.atari.prog.8bit.resource
Subject: Percom RFD Disk Drives Option Table
Posted-By: xx004 (Atari SIG)
Edited-By: xx004 (Atari SIG)
Date: Mon May 24 18:02:00 1999


I found the file PERCOMDD.DOC...


This file should be LISTed to a printer with the width being
set to 80 columns.  This file is intended for use by anyone
with Percom double density drives who wishes to know more about
what is on the ROM chip.  For furthur study of how these tables
are used, see the SAMPLE program on the diskette that is sent
with each Percom first drive system.






TM RFD 007                                20 SEPTEMBER 1982


TECHNICAL MEMO


PRODUCT: RFD DISK DRIVES
SUBJECT: OPTION TABLE


Percom RFD disk drives for the Atari home computers use an
intelligent disk controller.  In order to properly handle its
functions, a ROM chip containing an Option Table has been
developed.  This Option Table is located in a 1K RAM chip on
the controller board, and can be accessed by request from the
computer.

Below are tables which will help the programmer in
understanding the calls on the Percom controller.  Of
particular note are the bytes which handle the density of the
controller.

The Read Option and Write Option commands pertain to the 12
byte Option Table.  There is one table set up for each drive.

To access these tables, see the SAMPLE program on the Percom
Software Support diskette that comes with Percom Double Density
drive systems (NOTE: included on this disk as "PERCOMSM.PLE").


==============================================================
               INDIVIDUAL COMMANDS TABLE

FORMAT         21(hex)   FORMAT DISKETTE
RDOPT          4E        READ OPTION TABLE FOR A DRIVE (TABLE 2)
WROPT          4F        WRITE OPTION TABLE FOR A DRIVE (TABLE 2)
WRSECT         50        WRITE SECTOR WITHOUT VERIFY
               51        UNDEFINED
RESECT         52        READ SECTOR
RESTCM         53        READ STATUS MESSAGE (TABLE 3)
               54        UNDEFINED
               55        UNDEFINED
               56        UNDEFINED
               57        WRITE SECTOR WITH VERIFY

===============================================================



===============================================================
           OPTION TABLE TABLE 2

All 2-byte values are in MSB,LSB format, unlike the 6502
practice which uses LSB,MSB format.

  BYTE(S)        OPTION
   0        Number of tracks (This is a literal value)
   1        Step Rate (Standard 17xx FDC coding)

               value     rate
               -----     ----
                00        30 msecs.
                01        20 msecs.
                02        12 msecs.
                03        06 msecs.

   2,3      Sectors per track (This is a literal value)

   4        Number of Sides     0= 1 side
                                1= 2 sides
            any other values will cause unpredictable results


  5         Density             00= Single Density
                                04= Double Density

            any other values will cause unpredictable results

 6,7        Sector Size (bytes per sector.  This is a literal
            value)

 8          Drive Present       00= Drive is not present
            any other value indicates a drive is present

 9          ACIA      not currently implemented

Bytes 10 and 11 are reserved for future expansion

==============================================================


==============================================================
                     DRIVE STATUS TABLE 3

   BYTE            USE

   0    SYSTEM STATUS OF DRIVE

               value     status
               -----     ------
               32(dec)   sector size     0=128  1=256
               16        motor on?
               8         write protect
               4         FDC error
               2         data frame error
               1         cmd frame error

   1    FDC status

   2    Timeout for format- How long to wait for response to
        format

   3    Current track where read/write head is located


==============================================================

-END-





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\_________D /-/---_----'       mailto:mcheca@li.urp.edu.pe,
       _H__/_/            jtkirk@usa.net,JTKirk@HoTMaiL.com
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