HP Designjet Printers - About Hardware Handshaking
Describe the hardware handshaking for the HP Printer and Designjet family.
In a hardware handshake, the computer monitors one of the interface lines from the printer. The hardware handshake works as follows.
When the printer has room for data in its Input/Output (I/O) buffer, it signals the computer to send data by setting the Data Terminal Ready (DTR) line high (turning it on). The DTR line is pin 20 on the printer's RS-232-C connector. The printer raises the DTR line when either the I/O buffer has 40 more available bytes than the threshold level, or half the buffer is empty, whichever is smaller.
The printer has a threshold level that determines when the I/O buffer is in danger of overflowing and losing data. When the threshold level is reached, the printer sets the DTR line low (off).
note:When sending files or echoing data to the printer from a DOS prompt, hardware handshaking is used. DOS uses hardware handshaking exclusively. In addition, a cable that is pinned out for use solely with Xon/Xoff (a null modem cable) will not work.
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