Prevention Of Data Transfer Time-Out On The Host; Interface Selection; Ieee 1284.4 Protocol - Epson Photo750 Service Manual

EPSON Stylus Photo 750
1.3.5 Prevention of data transfer time-out on the
host
Generally, hosts abandon data transfer to peripherals when a peripheral
is in busy state for dozens of seconds continuously. To prevent hosts
from acting 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 starts when the remaining input buffer is less than several
hundreds of bytes. Finally, the printer is in busy state continuously when
the input buffer is full.

1.3.6 Interface selection

The printer has 3 built-in interfaces; Parallel I/F, Mac serial I/F and USB
I/F. 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 serial interface is not selected, the
interface sets the DTR signal MARK. When the printer is
initialized or returned to the idle state, the parallel interface got
into the ready state, the serial interface sets the DTR signal
SPACE. Caution that the interrupt signal such as the -INIT
signal on the parallel interface is not effective while that interface
is not selected.
Product Description

1.3.7 IEEE 1284.4 protocol

The packet protocol described by IEEE1284. 4 is supported on the
parallel I/F and USB I/F. Three function modes of IEEE1284.4 protocol,
"On", "Off" and "Auto" are available for each I/F, and one of them is
selected according to the value in EEPROM address 0Ah and 0Ch.
On: Communication in IEEE1284.4 packet mode is started by
receiving a magic string(1284.4 synchronous commands).
Until a magic string is received, other commdands are
discarded.
Off: Communication is carried out in the conventional mode. A
magnetic string(1284.4 synchronous commands) is discarded.
Auto: Communication is carried out in the conventional mode until a
magic string(1284.4 synchronous commands) is received. By
receiving a magic string, communication in IEEE1284.4 packet
mode is started.
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
operate over IEEE1284.
Parallel Interface
Revision A
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