Prevention Of Data Transfer Time-Out; Interface Selection; Ieee1284.4 Protocol - Epson PH890 Service Manual

EPSON Stylus PHOTO 890/1290

1.3.4 Prevention of Data Transfer Time-out

Generally, hosts abandon data transfer to peripherals when the peripheral is in the busy
state for dozens of seconds continuously. To prevent this kind of time-out, the printer
receives data very slowly, several bytes per minute, even if the printer is in the busy
state. The slowdown starts when the remaining input buffer becomes several hundreds
of bytes, and the printer finally gets into the busy state continuously when the input
buffer is full.
USB and IEEE1284.4 on the parallel interface do not require such function.

1.3.5 Interface Selection

The printer has two built-in interfaces: the USB and parallel interface.
These interfaces are selected automatically.
o
Automatic Selection
In this automatic interface selection mode, the printer is initialized to the idle state
while scanning which interface receives data when it is powered on. Then the
interface which received data first is selected. When the host stops data transfer
and the printer is in the stand-by state for seconds, the printer is returned to the idle
state. As long as the host sends data or the printer interface is in the busy state, the
selected interface is let as it is.
o
Interface State and Interface Selection
When the parallel interface is not selected, the interface gets into the busy state.
When the printer is initialized or returned to the idle state, the parallel interface
gets into the ready state. Note that the interrupt signal such as the -INIT signal on
the parallel interface is not effective while that interface is not selected.

1.3.6 IEEE1284.4 Protocol

The packet protocol described by IEEE1284.4 standard 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.
o
Automatic Selection
An initial state is compatible interface and starts IEEE1284.4 communication
when magic strings (1284.4 synchronous commands) are received.
PRODUCT DESCRIPTIONS
o
On
An initial state is IEEE1284.4 communication and data that received it by the time
it is able to take synchronization by magic string (1284.4 synchronous commands)
is discarded.
o
Off
An initial state is compatible interface and never starts IEEE1284.4
communication even if magic strings (1284.4 synchronous commands) are
received.
Interface
Revision B
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