Ieee1284.4 Protocol - Epson 890N - FX B/W Dot-matrix Printer Service Manual

EPSON FX-890/2190

1.2.7 IEEE1284.4 protocol

The packet protocol described by IEEE1284.4 is supported on the parallel I/F.
Two function modes of IEEE1284.4 protocol, "Off" and "Auto", are available and
one of them is selected according to the value of Default setting. (See Section
1.3.5. Default Setting).
NOTE:Packet protocol option "Off" &"Auto" in Default setting mode are effective in
not only parallel I/F but also USB I/F.
Auto: Communication is carried out in the convetional mode until a magic
string (1284.4 synchronous commands) is received. By receiving a
magic string, communication in IEEE1284.4 packet mode is started.
Off: Communication is carried out in the convetional mode.
NOTE:The packet protocol of IEEE1284.4 allows a device to carry on multiple
exchanges or conversations which contain data and/or control information
with another device at the same time across a single point-to-point link. The
protocol is not, however, a device control language. It does provide basic
transport-level flow control and multiplexing services. The multiplexed
logical channels are independent of each other and blocking of one has no
effect on the others. The protocol operates over IEEE1284.
PRODUCT DESCRIPTIONS Interface
Revision B
29