Deja News Toolbar
   
     [INLINE]  Desktops
     [INLINE]  Modems
     [INLINE]  Handhelds [INLINE]  Multimedia
   [INLINE]  Scanners
   [INLINE]  Notebooks [INLINE]  Software
   [INLINE]  Printers
   [INLINE]  Upgrades [LINK] 
   
   message/thread
   
   Message 54 of 100 for search * 
   return to search results help
   
   Re: (Ultra Slow Speed?) Re: 5 1/4 hd disks usuable?
   Author:   John Iannetta <73510.2152@CompuServe.COM>
   Date:   1999/03/19
   Forum:   comp.sys.cbm
   
   computerliteracy.comFind books on
   *
   
   more headers author posting history post reply prev next 
   _________________________________________________________________
   
    John/Lori said,

"Wouldn't it be simpler to try to bump up the write current?
perhaps there's a spare bit in one of the CIAs that could be used for
switching the write current for different disk media?".

    Good idea!  Here's something that might work.
------------------------------------------------------------------------------

                            o + 5VDC
                            I
                            I
-----i      i---------------i-i
     I      Io       U        I
   2 I------I 1            14 I
     I      I                 I
 UC1 I i----I 2            13 I
-----! I    I                 I
       I----I 3            12 I
       I    I      7406       I
       I i--I 4            11 I
       I I  I                 I
       I I  I 5            10 I
       I <  I                 I
2.2    I <  I 6             9 I-------i
kohm,  I <  I                 I       I
1/4 W, I <  I 7             8 I----i  I
5%     I <  I                 I    I  I
       I I  !-i---------------!    I  I
       I I    I                    I  I
       I I    o GND                I  I
       I I                         I  I
       I i----I<--- CR6            I  I
-----! !---------------------------!  I
     I                                I
  39 I--------------------------------!
     I
 UC3 I
-----!

------------------------------------------------------------------------------

    The circuit is for the "short board" 1541; UC1 is the PLA, and UC3 is
VIA1.  CA2 (pin 39) of UC3 is not used by the 1541 DOS, and is here used to
control "HD" mode (High Density, active low).  That pin is controlled by
register $0C of VIA1, which DOS writes to only on reset (hardware or software).
After a reset, pin 39 may be taken high (HD mode OFF), with:

open15,8,15,"m-w"+chr$(12)+chr$(24)+chr$(1)+chr$(15):close15

or taken low (HD mode ON) with:

open15,8,15,"m-w"+chr$(12)+chr$(24)+chr$(1)+chr$(13):close15

In HD mode, the write current is doubled (10 mA, rather than 5 mA).  The erase
current is NOT changed, so there could be a problem with HD disks that have
been preformatted (using MFM).  The resistor connects to the cathode of CR6,
located near UF3.

--
I pressed RETURN, and the message said, "Missing GOSUB".

                          John
   _________________________________________________________________
   
   view for bookmarking
   text only mail this message to a friend
   Sponsored by ComputerLiteracy.com post reply     << prev · next >> 
   subscribe to comp.sys.cbm
   
   SPONSORED LINKS
        Yellow Pages ·  Compare hardware prices! ·  5¢ long distance
    AutoConnect ·  Free Stuff  ·  Trade with Datek  ·  GET IT NOW @ NECX
         FREE downloads! ·  <<Shopping>> ·  Auctions & Classifieds
                                      
                                      
      Home  ·  Communities  ·  My Deja News  ·  Power Search  ·  Post
                                      
              About Deja News  ·  Ad Info  ·  Our Advertisers
            ____________________________________________________
   
   Copyright © 1995-99 Deja News, Inc. All rights reserved.
   Conditions of use  ·  Site privacy statement reviewed by TRUSTe