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upde     inc  d                 
         ld   a,d               
         and  7                 
         ret  nz                
         ld   a,e               
         add  a,32              
         ld   e,a               
         ld   a,d               
         ret  c                 
         sub  8                 
         ld   d,a               
         ret

Slower alternative:

upde      ld   a,d               
          dec  d                 
          and  7                 
          ret  nz                
          ld   a,e               
          sub  32                
          ld   e,a               
          ld   a,d               
          jr   c,upde2           
          add  a,8               
          ld   d,a               
upde2     cp   64                
          ret  nc                
          ld   d,87               
          ret

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