Parallel

Interface Modes

Byte Mode

Printer-host communication is done in bytes.The byte mode may be used by the host device in a DMA (Direct Memory Access) mode for more efficient operation.

When byte transfer is complete and there is no more data to transmit, the host may do one of the following:

nTerminate and return to the compatibility mode.

nStay in the Host Busy, Data Not Available phase.

nSet Host Busy Low, putting the interface into the idle phase. If there is additional data, the host may do one of the following:

nSet Host Busy Low, indicating that the host can accept additional data.

nStay in the Host Busy, Data Not Available phase.

nTerminate and return to the compatibility mode.

Check your host documentation to see if the host is 1284 compatible.

Compatibility Mode

Printer-host communication is done in a manner that ensures com- patibility.

ECP (Enhanced Compatibility Port) Mode

This is an advanced version of byte mode which allows transfer of data in either direction without returning to the compatibility mode. The communication is a half-duplex channel with either device, the host or the printer, making a request for data transfer when there is available data. In the case of simultaneous requests for transfer, the printer always defers to the host.

Additional Technical Information

5-31