Prevention Of Data Transfer Time-Out; Interface Selection; Ieee1284.4 Protocol - Epson Stylus PHOTO 1270 Service Manual

EPSON Stylus PHOTO 870/1270

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.
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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.
"
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
PRODUCT DESCRIPTIONS
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.
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Automatic Selection
An initial state is compatible interface and starts IEEE1284.4
communication when magic strings (1284.4 synchronous commands)
are received.
"
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.
"
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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