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Termination
Termination is the process of returning to Compatibility mode from the Nibble or Byte modes. When performing Termination,
the host sets the signals as follows:
• IEEE 1284 Active (nSelectln): Low
• HostBusy (nAutoFd): High (Event 22)
There are two methods of Termination:
(1) Termination through a handshake between the host and the printer
(2) Immediate termination
(1) Termination through a handshake between the host and the printer:
When switching from Reverse mode to Compatibility mode, this termination method can be used if the interface is
activated (IEEE 1284 Active: High) and Event 22 has taken place.
1) The printer responds to IEEE 1284 Active by setting PtrBusy (Busy) and nDataAvail (nFault) to High. (Event 23)
2) The printer then inverts Xflag (Select) and sets PtrClk (nAck) to Low. (Event 24)
3) The host sets HostBusy (nAutoFd) to Low. (Event 25)
4) The printer returns nDataAvail (nFault), Xflag (Select), and AckDataReq (PError) to the status given in the
Compatibility mode, and sets PtrClk (nAck) to High. (Events 26 and 27)
5) The host sets HostBusy (nAutoFd) to High to terminate the handshake and return the interface to the Compatibility
Mode Idle phase. (Event 28)
6) The printer changes PtrBusy (Busy) to be able to receive data from the host.
(2) Immediate termination:
1) If the interface is deactivated (IEEE 1284 Active: Low) without Event 22 having taken place, the printer immediately
performs Termination. In this termination, the data is not guaranteed, and the printer switches the data bus from output
to input within 1 µsec.
In the Reverse Idle phase, the printer can notify the host that it has data to transfer to the host. The notification may
occur simultaneously with termination in order for the host to move from the Idle phase to the Compatibility mode.
If the printer has data to send, it initiates the Interrupt phase indicated by Events 8 and 9. In this case, if 1284 - Active
(nSelectIn) was set to Low before HostBusy (nAutoFd) changed from High to Low, the printer interprets that the host
has switched to the Termination phase, and then completes the normal termination through handshaking.
