QMS 1725E, Reference

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PS Protocol
Option
QMS 1725E Print System Reference 5-26
Check your host documentation to see if the host is 1284 compatible.
Compatibility Mode
Printer-host parallel communication is done in a manner that ensures
compatibility.
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 parallel 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.
EPP (Enhanced Parallel Port) Mode
Printer-host parallel communication is done via asynchronous bidirec-
tional eight-bit transfer. A return to compatibility mode is not required.
Nibble Mode
Printer-host parallel communication is done in nibbles (four bits; one-
half byte) with the low order nibble sent first. A transfer of two nibbles
is required for each byte of information.
PS Protocol Option
Your QMS 1725E Print System supports PS Protocol, a new protocol
for communication between the printer and a host computer over the
serial, parallel, and optional interfaces. This binary communications
protocol (BCP) allows any 8-bit binary value (0-255) to be treated as
data, while allowing a few of the values to function as special control
characters. When communicating 8-bit binary data in binary or binary
fixed mode, the printer uses the quoting mechanism of the binary