Prevention Hosts From Data Transfer Time-Out; Interface Selection; Ieee1284.4 Protocol - Epson Stylus PHOTO 2000P Service Manual

EPSON Stylus PHOTO 2000P

1.3.1.4 Prevention Hosts from Data Transfer Time-out

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

1.3.1.5 Interface Selection

The printer has 2 built-in interfaces; the USB and parallel interface.
These interfaces are selected automatically.
- Automatic selection
In this automatic interface selection mode, the printer is initialized to the
idle state scanning which interface receives data when it is powered on.
Then the interface that receives data first is selected. When the host stops
data transfer and the printer is in the stand-by state for the seconds, the
printer is returned to the idle state. As long as the host sends data or the
printer interface is busy state, the selected interface is let as it is.
- Interface state and interface selection
When the parallel interface is not selected, the interface got into the busy
state. When the printer is initialized or returned to the idle state, the
parallel interface got into the ready state. Caution that the interrupt signal
such as the -INIT signal on the parallel interface is not effective while that
interface is not selected.
Product Descriptions

1.3.1.6 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 operate over IEEE1284.
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 A
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