Epson EPL-N1200 Reference Manual page 182

reverse data transfer phase: In nibble mode, this signal serves as nibble
data bit 3 and then 7.
reverse idle phase: Reflects the BUSY status of the forward channel.
ECP mode: Used for forward direction flow control. In reverse direction,
this signal is used as a ninth data bit that indicates whether the data
signals indicates a command or data.
PError/AckDataReq/nAckReverse
Compatibility mode: High signal indicates that a feed jam occurred in the
paper supply section, or that there is no paper in the paper tray.
negotiation phase: High signal indicates whether or not IEEE 1284 is
supported or not. Afterwards, this signal conforms with nDataAvail
(nFault).
reverse data transfer phase: In nibble mode, this signal serves as nibble
data bit 2 and then 6.
reverse idle phase: High until the host requests a data transfer.
Afterwards, this signal conforms with nDataAvail (nFault).
ECP mode: Low signal authorizes nReverseRequest. The host looks at this
signal in order to determine whether or not it has permission to drive the
data signals.
Select/Xflag
Compatibility mode: Always high.
negotiation phase: Xflag indicates the extensibility flag. Used to respond
to the extensibility request value sent from the host.
reverse data transfer phase: In nibble mode, this signal serves as nibble
data bit 1 and then 5.
reverse idle phase: Same as negotiation phase.
ECP mode: Same as negotiation phase.
Technical Specifications
A-9