Oki ML3390, Руководство пользователя

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D-33
Appendix D: Interface Data
- +
- +
D+ 9
D– 10
B+ 18
B– 19
GND 7
A
B
A
B
SP4
SP5
A B
SP5
C A B
A B
SP3
SP4
A B
SP2
A B
SP1 Centronics Blocked Duplex
Connection: 2-wire
Power source receive loop: Printer
Power source send loop: None
Host Printer Assignment of
Short-Circuit Jumper
Technical note
Diagram 14
In combination with this circuit you can only use the Centronics
Blocked Duplex protocol in order to ensure the correct transmission
of data.
One must differentiate between 2-wire-connections (see diagram 13
and 14) and circuits in which only the receive loop D+ -> D- of the
printer is connected. Strictly speaking these are 4-wire circuits (see dia-
gram 8 to 11), in which the send loop B+ -> B- of the printer is not
integrated in the circuit. It is therefore not possible to control the print-
er status (Ready to Receive or Receive Buffer Full).
This circuit is often used by measuring systems and unit controls to
which a log printer is connected. Received data is printed immediately
without having to store it in the buffer. Even if a low transmission rate
is used, no data is lost.
To ensure a constant power supply of 15 mA to 20 mA, the wire resist-
ance as well as the number of electronic components in the current
loop has to be considered. This means that the appropriate current
control resistors of the power source used have to be adjusted to the
prevailing electrical conditions on either the printer or the computer.
The above mentioned procedures should only be carried out by
trained technicians referring to the technical documentation (circuit
diagrams etc.) of the printer interface and the computer interface.