Epson EPL-5700 Reference Manual page 96

Reverse data transfer phase: In nibble mode, setting this signal
low indicates to the printer that the host is ready to receive data.
When this signal is subsequently set high, it indicates that the host
received the data.
Reverse idle phase: This signal is set high in response to a PtrClk
(nAck) low pulse in order to return to the reverse data phase. If
this signal is set high at the same time that IEEE 1284active
(nSelectln) is set low, the IEEE 1284 idle phase is aborted and the
interface returns to compatibility mode.
ECP mode: Used for reverse direction flow control. Also used for
handshaking via PeriphClk (nAck).
NC
Not used
PeripheralLogicHigh
Parallel B: NC
Parallel C: Pull up to +5V with 3.9 K
nlnit/nReverseRequest
Compatibility mode: When a low signal is detected, the printer is
deemed to be BUSY until the low signal is released.
Negotiation phase: Always high
Reverse data transfer phase: Always high
ECP mode: Low when switching to reverse direction. The
peripheral device has permission to drive the data signals only
when this signal is low and 1284 active is high.
nFault/nDataAvail/nPeriphRequest
Compatibility mode: Low signal indicates that an error occurred.
A-10
Technical Specifications