Interface Selection; Prevention Of Hosts From Data Transfer Time-Out; Ieee1284.4 Protocol - Epson LX-300+II RTP Service Manual

EPSON LX-300+II/300+II RTP/1170II

1.3.5 Interface Selection

The printer has 3 interfaces; the parallel interface, the serial interface and the USB interface.
These interfaces are selected manually by Default Setting or selected automatically.

Manual Selection
One of 3 interfaces can be selected by Default setting.

Automatic Selection
The automatic interface selection is enabled by Default Setting. 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 stand-by
state for the period of seconds specified by Default Setting, the printer is returned
to the idle state. As long as the host sends data or the printer interface is busy state,
printer keeps the interface selection status as it is.

Interface State and Interface Selection
When the parallel interface is not selected, the interface gets into a busy state.
When the USB interface is not selected, the interface responds to an OUT
transaction with NAK handshake. When the serial interface is not selected, the
interface sends XOFF and sets the DTR signal MARK. When the printer is
initialized or returned to the idle state, the parallel interface get into a ready state,
the USB interface become to respond to an OUT transaction with ACK handshake,
the serial interface sends XON and sets the DTR SPACE. Caution that the
interrupt signal such as a -INIT signal on the parallel interface and software reset
on the USB interface is not effective while that interface is not selected.

1.3.6 Prevention of Hosts from Data Transfer Time-out

Generally, hosts abandons data transfer to peripherals when a peripheral is in 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. At
last, when the input buffer is full, the printer is in busy state continuously.
NOTE: This prevention basically operates on the parallel I/F and on the USB I/F.
NOTE: IEEE1284.4 on the parallel interface and that on the USB interface do
not require this function.
PRODUCT DESCRIPTION

1.3.7 IEEE1284.4 protocol

The packet protocol described by IEEE1284.4 is supported on the parallel I/F and the USB
I/F.
Two function modes of IEEE1284.4 protocol, "Off" and "Auto", are available and one of
them is selected according to the value of Default setting. (See 1.4.2.3 "Default Setting")
NOTE: Packet protocol option "Off" & "Auto" in Default setting is effective in
not only parallel I/F but also USB I/F.
NOTE: In the case that data is printed from printer driver of Windows-based PC,
select the packet protocol to "Auto".
NOTE: The function mode of IEEE1284.4 protocol "Off" is not guaranteed only
on the USB I/F.

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.

Off:
Communication is carried out in the conventional mode.
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 operates over
IEEE1284.
Interface Specifications
Revision D
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