Black Box PI405A, Руководство пользователя, Страница: 16 / 19

13
DATABUFFER PLUS
4.1.2 LED
S
Four 7-segment LEDs are located on the front panel of the DataBuffer Plus. These
LEDs are similar to a digital-clock display. The LEDs continuously display the
amount of data in the buffer in kilobytes. These LEDs also aid you when you preset
multiple copies. You don’t have to remember how many copies you set, simply
press the Copy/Pause button again and the LEDs will give you a digital display
of the amount.
4.1.3 C
OPY
/P
AUSE
B
UTTON
Presetting multiple copies. First, press the Reset button to clear all previous settings.
Before you send the data, depress the Copy/Pause switch once for each copy you
want printed. For example, if you want 10 copies of a document, press the
Copy/Pause button 10 times before sending the document to the DataBuffer Plus.
The LED displays the number of copies set each time you add a copy. You can set
the unit to print up to 999 copies.
Printing one additional copy. For one additional copy of the data you just sent, press
the Copy/Pause button. One copy of the most recent job sent to the buffer is sent
to the printer. The LEDs display the original number of preset copies. As you add
copies, the LEDs display your changes. If a 7-second time period of inactivity on
the input port occurs, the unit considers it the end of a print job.
Stopping data output. Pressing Copy/Pause while data is being sent stops the output of
data from the buffer while allowing data input to continue. The buffer remains in
the “Pause” mode until you press Copy/Pause again. The LED display gives a readout
of the current buffer status and flashes to indicates the unit is in pause mode.
4.2 Handshaking
The DataBuffer Plus usually accepts data much faster than the output devices
(such as printers) to which it is attached. Handshaking is a form of flow control
that prevents the unit’s output from overrunning the printer’s ability to accept
the data.
Data loss is prevented if equipment connected to the input and output serial
ports support hardware or X-ON/X-OFF handshaking.
4.2.1 H
ARDWARE
H
ANDSHAKING
When the unit’s buffer is nearly full on the input end, it changes Pin 20 from a
high voltage to a low voltage. When the output device (printer) has emptied the
unit’s buffer so that more input data can be accepted, the DataBuffer Plus raises
Pin 20 to a high-level signal.