CP/M   V2.2, Patch 09, DEBLOCK.ASM, 2/11/82

          Copyright  1982 by Digital Research, Inc., Pacific Grove, CA  93950


          Program:  DEBLOCK.ASM

          Error Description:

               The following modification affects only CP/M  systems  that  use
          the  optional blocking and deblocking algorithms listed in Appendix G
          of the CP/M Alteration Guide.  The  sector  blocking  and  deblocking
          algorithms   provided   in  the  guide  work  improperly  in  certain
          circumstances.

          Patch Procedure:

               Use the CP/M text editor to insert the following changes:


                    Following the comment on line 111 of Appendix G:

                          "read the selected CP/M sector"

                    Insert the following two lines:

                          xra     a            ;accum = 0
                          sta     unacnt       ;unacnt = 0

                    The next source lines remain as shown:

                          mvi     a,1
                          sta     readop       ;read operation

                    Insert the following code in your BIOS Home routine:

                     home:
                          lda     hstwrt       ;check for pending write
                          ora     a
                          jnz     homed
                          sta     hstact       ;clear host active flag
                     homed:

                    Continue with the rest of the home routine.



               Licensed users are granted the right to include these changes in
          CP/M software.  CP/M is a registered trademark of Digital Research.