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DX20LD.DOC -- Changes from V4(4) to V4(5)
October 1981






























COPYRIGHT (C) 1978,1980,1982 BY
DIGITAL EQUIPMENT CORPORATION, MAYNARD, MASS.


THIS SOFTWARE IS FURNISHED UNDER A LICENSE AND MAY BE USED AND  COPIED
ONLY  IN  ACCORDANCE  WITH  THE  TERMS  OF  SUCH  LICENSE AND WITH THE
INCLUSION OF THE ABOVE COPYRIGHT NOTICE.  THIS SOFTWARE OR  ANY  OTHER
COPIES  THEREOF MAY NOT BE PROVIDED OR OTHERWISE MADE AVAILABLE TO ANY
OTHER PERSON.  NO TITLE TO AND OWNERSHIP OF  THE  SOFTWARE  IS  HEREBY
TRANSFERRED.

THE INFORMATION IN THIS SOFTWARE IS SUBJECT TO CHANGE  WITHOUT  NOTICE
AND  SHOULD  NOT  BE  CONSTRUED  AS  A COMMITMENT BY DIGITAL EQUIPMENT
CORPORATION.

DIGITAL ASSUMES NO RESPONSIBILITY FOR THE USE OR  RELIABILITY  OF  ITS
SOFTWARE ON EQUIPMENT WHICH IS NOT SUPPLIED BY DIGITAL.

DX20LD.DOC                                                      Page 2


DX20LD.DOC -- Changes from V4(4) to V4(5)
October 1981



1.0  SUMMARY

The DX20 is a microcoded device that must have its microcode down-line
loaded.   Any  DX20's  on  a  system  are automatically loaded by BOOT
whenever TOPS-20 is  manually  loaded  by  the  operator.   Sometimes,
however,  it  is desirable to manually reload the DX20 microcode while
TOPS-20 is up and running.  The DX20LD program is designed to  perform
this manual reload of the DX20 microcode.

The DX20 comes in two basic types:

     1.  1 for TU70-series tape drives (type DX20A).

     2.  1 for RP20 disk drives (type DX20B).

(Note that the type, channel # and unit # of each DX20 are reported on
the  CTY by BOOT when it reloads the DX20's during a manual restart of
TOPS-20.   During  an  auto-restart  of  TOPS-20,  only  DX20B's   are
reloaded.)

Corresponding to these two types of DX20's are two types of microcode:

     1.  TU70-series microcode:         in file DXMCA.ADX

     2.  RP20 microcode:                in file DXMCE.ADX



2.0  EXTERNAL CHANGES

If your system has only one DX20 on it (or only one of  each  type  of
DX20),  then  you  need only specify the appropriate microcode file as
follows (assuming you have a TU70-series DX20):

     @DX20LD
     File:  DXMCA.ADX<RET>

If you have more than 1 of the same type DX20 (2  TU70-series  DX20's,
say),  then you must specify the channel number and the DX20 number of
the particular DX20 you want to reload:

     @DX20LD
     File:  DXMCA.ADX/D:12<RET>

The /D switch, shown in the above example is of the form /D:mn,  where
"m"  is  the  channel  number  (RH20 controller #) and "n" is the DX20
number of the DX20 that should be reloaded.

DX20LD.DOC                                                      Page 3


Ordinarily, the filename is sufficient to identify to DX20LD, the type
of  DX20  (tape  or  disk)  to  be reloaded.  Any filename of the form
"DXMCAxxxxxxxx.ADX" indicates microcode for a TU70-series  DX20  while
any  filename  of the form "DXMCExxxxxxxx.ADX" indicates microcode for
an RP20 DX20.  If, for some reason, it is necessary to load  microcode
from a file whose name does not follow these conventions, then /T (for
TU70-series  tape  drives)  or  /R  (for  RP20  disk  drives)  may  be
specified.  (Be careful, as it is possible to force DX20LD to load the
wrong type of microcode for a given DX20.)


File summary:

DXMCA.ADX                TU70-series DX20's (DX20A)
DXMCE.ADX                RP20 DX20's (DX20B)

Switch summary:

/D:mn          Load microcode for channel "m", DX20 "n"
/T             Load microcode only for TU70-series DX20's
/r             Load microcode only for RP20 DX20's


When to reload the DX20:

     1.  When the DX20 microcode stops -  giving  BUGCHK's  DXBDMI  or
         DXBDIE, or BUGINF DX2HLT.

     2.  Power-fail restart  caused  by  line  interference  or  power
         spikes.

     3.  Someone has manually powered-down the DX20.

     4.  Auto-reload of operating system  (necessary  to  reload  only
         DX20A's - BOOT will automatically reload DX20B's).


When not to reload the DX20:

     Never make a pratice of reloading a DX20 while  it  is  currently
     performing IO transfers - there is a posibility of writing random
     data to a tape or disk.  In  the  latter  case  you  could  cause
     damage to the disk structure.

DX20LD.DOC                                                      Page 4


3.0  KNOWN BUGS AND DEFICIENCIES

None.



4.0  INSTALLATION INSTRUCTIONS


4.1  Files Needed to Run DX20LD

     SYS:DX20LD.EXE
     SYS:*.ADX


4.2  Instructions for Loading and Installing DX20LD

Mount the tape labeled  Installation  Tape  on  MTA0:   and  type  the
following commands:

     SKIP MTA0:5 FILES
     R DUMPER
     TAPE MTA0:
     REWIND
     DENSITY 1600-BPI
     SKIP 1
     RESTORE <*>DX20LD.EXE (TO) SYS:*.*.-1
     REWIND


4.3  Files Needed to Build DX20LD

DX20LD is built from the following file:

     DX20LD.MAC

In addition, the following files must be on SYS:

     MACREL.REL
     MACSYM.UNV
     MONSYM.UNV

DX20LD.DOC                                                      Page 5


4.4  Instructions for Building DX20LD

Mount the tape labeled Distribution on MTA0:  and type  the  following
commands:

     R DUMPER
     TAPE MTA0:
     REWIND
     DENSITY 1600-BPI
     SKIP 1
     RESTORE <*>*.*.* (TO) <self>*.*.*
     REWIND
     ^C
     SUBMIT DX20LD.CTL/TIME/UNIQ:0/REST


4.5  Special Considerations

The file which contains the DX20 microcode and is loaded by DX20LD  is
SYS:DXMCA.ADX   for   non-RP20  sites.   For  the  RP20  sites  it  is
SYS:DXMCE.ADX.



5.0  INTERNAL CHANGES

Refer to DX20LD.TCO for detailed information about internal changes.



6.0  SUGGESTIONS

None.



[End of DX20LD.DOC]