Epson Stylus COLOR 900 Service Manual page 29

EPSON Stylus COLOR 900/900N
Interface State and Interface Selection
Y
When an interface other than the parallel interface is selected, the
parallel interface goes into the BUSY state.
Y
When an interface other than the serial interface is selected, the
serial interface sets the DTR signal to MARK.
Y
When an interface other than the optional or Ethernet interface is
selected, the printer sets the "OFF LINE" bit of the MNSTS register
for the optional interface.
Y
When the printer is initialized or returns to the idle state, the parallel
interface enters the ready state, the serial interface sets the DTR
signal to SPACE and the printer resets the "OFF LINE" bit of the
MNSTS register for the optional interface.
NOTE: An interrupt signal, such as /INIT, on the parallel interface is not
effective when that interface is not selected.
1.3.7.1 IEEE 1284.4 Protocol
The packet protocol described by the IEEE1284.4 standard allows a
device to carry on multiple, simultaneous exchanges containing data
and/or control information with another device across a single, point-to-
point link. The protocol is not, however, a device control language. It
provides basic transport-level flow control and multiplexing services.
The multiplexed logical channels are independent of each other and the
blocking of one has no effect on the others. The packet protocol
operates over IEEE1284.
Y
Automatic selection:
The compatible interface is in an initial state and IEEE1284.4
communication starts when it receives magic strings (1284.4
synchronous commands).
Y
ON:
IEEE1284.4 is enabled in the initial state. Data sent before the
magic string (1284.4 synchronous commands) is discarded.
Y
OFF:
IEEE1284.4 is disabled and IEEE1484.4 synchronous commands
are ignored. The compatible interface is in the initial state.
Chapter 1 Product Description
24