LQ-300 Service Manual
Product Description
1.3.3 Interface Selection
The printer has 2 interfaces: parallel and serial.
These interfaces can be selected manually in
default-setting mode or selected automatically.
●
Manual selection
One of the two interfaces can be selected in default-setting mode.
. Automatic selection
When automatic interface selection is enabled in default-setting mode, the printer is
initialized to idle state scanning, in which an interface receives data when it is powered
on, and the interface that receives data first is selected. When the host stops data transfer,
and the printer is in the standby state for 10 or 30 seconds (time selectable in the
default-setting mode), the printer returns to the idle state. As long as the host sends data
to the printer interface in the BUSY state, the currently selected interface remains the
same.
. Interface state and interface selection
When the parallel interface is not selected, the interface is in the BUSY state. When the
serial interface is not selected, the interface sends X-OFF and sets the
DTR
signal MARK.
When the printer is initialized or returned to the idle state, the parallel interface is in a
READY state, the serial interface sends X-ON and sets the
DTR
signal SPACE. Notice
that the interrupt signal such as a INIT signal on the parallel interface is not effective
while that interface is not selected.
1.3.4 Preventing the Host from Data Transfer Timeout
Hosts abandon attempts at data transfers to peripherals when a peripheral is in BUSY state for
dozens of seconds continuously. To prevent hosts from this
ldnd
of timeout, 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, when the
input buffer is full, the printer goes into the BUSY state continuously.
Rev. A
1-15
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