Epson 8900 Series manual Parallel Interface Communication Protocol

Paper-Empty Signal

The paper-empty (PE) signal from the printer indicates that the paper supply is empty. The printer activates this signal in combination with the fault signal to indicate the paper-empty condition to the host.

Select Signal

The select (SLCT) signal from the printer indicates to the host that the printer is online and ready to receive data. The completion of either a normal power-up operation or a host-generated initialization cycle activates SLCT.

Verify Signal

The verify signal confirms proper connection of the parallel interface cable between the host and the printer. The verify in (VFIN) and verify out (VFOUT) pins are connected together inside the printer to form a loopback circuit. The host sends VFIN to the printer and, if the cable is connected properly, the printer returns the signal as VFOUT.

Ground Signals

The logic ground (LGND) connects to the printer power supply logic ground to provide a common reference point for all interface signals. The chassis ground (CGND) connects to the ac power cord safety ground to provide protection for the printer and personnel.

Parallel Interface Communication Protocol

The parallel interface communication protocol is a set of conventions that ensures compatibility between the printer and the host computer. The following paragraphs describe these conventions.

Data-Transfer Timing

Because the parallel interface transfers all bits of a character simultaneously, correct timing is important to prevent data loss or corruption. When the host senses that BUSY is inactive (low), the host can initiate a character-transfer cycle on the interface.

Communication Interfaces 10-10