Epson C I - 4 0 4 0, C I - 4 0 5 0 user manual Transmission Protocol Description, Timing

Appendix A System Interface Description

2.2Transmission Protocol Description

After Power-ON the PE (Paper Empty) signal is set to low level and the SELECT and FAULT¯¯¯¯¯signals are set to high level.

The printer is now ON-LINEand ready to receive data.

Timing

The host sets a print/control character to the 8 data lines.

After a time delay of a minimum of 0.5 µs, the host sends a STROBE¯¯¯¯¯¯ pulse of a minimum of 0.5 µs. When the data byte is accepted into the interface buffer the printer transmits a BUSY signal and an ¯¯¯¯ACKN pulse.

The ¯¯¯¯ACKN pulse informs the host that the data has been received and that the printer is ready to receive new data.

If the interface buffer is full except for the last character the BUSY is not reset in order to stop the data transfer from the host. The BUSY signal is only reset if space is available in the interface buffer for a minimum of 512 characters.

While the printer is offline, or a serial interface is active BUSY remains high and no ¯¯¯¯ACKN is sent until the printer enters online state or the serial interface is deselected.

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