Optional Interface; Interface Selection; Prevention Host From Data Transfertimeout - Epson DLQ-3000 Service Manual

Product Description

1.3.3 Optional Interface

Type-B and Type level 2 optional interfaces are available except for C82305 and C82306 serial
interface.

1.3.4 Interface Selection

The printer has 3 interfaces; the parallel interface, serial interface and optional interface. These
interfaces are selected manually by SelecType or selected automatically.
Manual selection
One of 3 interfaces can be selected by SelecType.
Automatic selection
The automatic interface selection is enabled by SelecType. In this automatic interface selection
mode, the printer is initialized to the idle state scanning in which interface receives data when it is
powered on. The interface that receives data first is selected. When the host stops data transfer,
the printer is returned to idle state. As long as the host sends data to 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 is in a BUSY state. When the serial
interface is not selected, the interface sends XOFF and sets the DTR signal MARK. When the
optional interface is not selected, the printer sends disable commands to the optional interface.
When the printer is initialized or returned to the idle state, the parallel interface is in a READY
state, the serial interface sends XON and sets the DTR SPACE and the printer sends enable
commands to the optional interface. Notice that the interrupt signal such as a -INIT signal on the
parallel interface is not effective while that interface is not selected.
1.3.5 Prevention Host from Data Transfer Timeout
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 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. At last, when the input buffer
is full, the printer is continuously in BUSY state.