Epson TM-U950P - B/W Dot-matrix Printer Specification page 151

In this interface, the printer status after power-on sequence is available by checking Logic-
HIGH.
In 500 ms after Logic-HIGH exceeds High level (3.0 V) following the power-on sequence, all
signals become active.
The printer may be forcedly reset through the nInit signal. However, in either of the following
conditions, the forced printer reset becomes inoperative and Low level pulses are ignored.
• When the 1284-active(Select-In) singal is High.
J.2.3.1 Description
The Compatibility Mode features compatibility with the Centronics interface popular among
the existing PCs. This is the initialization mode of the interface following the power-on
sequence and also the printer reset. Under normal condition, the printer receives data from
the host in this mode.
Data transmissions are proceeded as follows.
• The host checks that the printer has been ready for data acception then sends data and the
Strobe signal.
• Upon detection of Strobe signal from the host, the printer responds by setting Busy high to
receive transmitted data.
• After completion of data reception, the printer sends the nAck LOW pulse signal and sets the
Busy signal low.