Epson DFX-8500 service manual Interface Selection, Prevention Hosts from Data Transfer Time-out

GENERAL DESCRIPTION

1.3.5 Interface Selection

The printer has three interfaces; the parallel interface, serial interface, and optional Type-B interface. These interfaces are selected manually by DIP SW or selected automatically.

‰￿ Manual selection:

￿One of three interfaces can be selected by DIP SW setting.

‰￿ Automatic selection:

The automatic interface selection is enabled by DIP SW 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 seconds specified by DIP SW setting, 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 a busy state. When the serial interface is not selected, the interface sends X-OFF 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 got into a ready state, the serial interface sends X-ON and sets the DTR SPACE and the printer sends enable commands to the optional interface.

Caution that the interrupt signal such as a /INIT signal on the parallel interface is not effective while that interface is not selected.

1.3.6 Prevention 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.

Rev. B 1-23