The Parallel Port: Termination of a 1284 Mode



Byte and Nibble Mode Termination

A 1284 compliant peripheral device must implement this sequence.

For EPP mode termination and ECP mode termination are different. The following diagram shows the standard termination sequence for byte and nibble modes.

   /Select   /AutoFeed   /Ack  
   1284Active   HostBusy   PtrClk  
  
  h  
  
  u  
  
  h  
  
black separator
1  
  hl  
  
  uh  
  
  h  
   H signals begin of termination sequence
2  
  l  
  
  h  
  
  hl  
   P signals acknowlegdement
3  
  l  
  
  hl  
  
  l  
   H signals end of termination sequence
4  
  l  
  
  l  
  
  lh  
   P signals acknowlegdement
black separator
5  
  l  
  
  lk  
  
  h  
   H sets /AutoFeed to desired value
  
  l  
  
  k  
  
  h  
   H and P are now in compatibilily mode again

EPP Termination

This termination sequence is quite trivial and can probably terminate byte and nibble modes, too, because it uses the /Init line, which should reset the printer. Only in ECP mode, this does not work, since ECP uses the /Init line as a normal signal.

   /Init   /Select  
      1284Active  
  
  u  
  
  u  
  
black separator
1  
  ul  
  
  u  
   H signals begin of termination sequence
2  
  l  
  
  u  
   H waits for >=50us
3  
  lh  
  
  uh  
   H selects device
black separator
  
  h  
  
  h  
   H and P are now in compatibilily mode again

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January 14th, 2013
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