Fujitsu DL7400 Manual Do Utilizador

A protocol is a set of instructions that control the way data is transmitted 
between devices such as a computer and printer.  The protocol ensures 
that the computer does not send information to the printer faster than the 
information can be processed.  By telling the computer when the printer 
can receive data, the protocol prevents the printer s buffer from 
overflowing. 

This printer offers a choice of four different protocols for connection to a 
variety of computers:  XON/XOFF, DTR, and RC.  If you computer 
documentation does not recommend a particular protocol, try DTR.  The 
following table describes the three protocols. 

XON/XOFF
(DC1/DC3) 

When the printer is ready to receive data, it sends the 
XON (DC1) code (hex 11).  When fewer than 255 bytes 
of space remain in the buffer (or when the printer is taken 
offline), the printer sends the XOFF (DC3) code (hex 13). 
(When the input buffer is configured for 256 bytes, the 
buffer limit is reduced from 255 bytes to 63 bytes.)  The 
computer must stop transmitting data within 255 (63)  
characters of receiving the XOFF code, or information 
may be lost.  If paper runs out, the printer sends an NAK 
code (hex 15). 

DTR 

DTR is a hardware protocol; that is, the DTR signal on 
interface cable pin 20 is used to control the flow of data 
rather than transmission of a character code.  When the 
printer is ready to receive data, pin 20 is high.  When 
fewer than 255 (63) bytes of space remain in the buffer 
(or when the printer is taken offline), pin 20 is low.  The 
computer must stop transmitting data within 255 (63) 
characters of DTR being low, or information may be lost.  

RC 

The RC protocol is the same as the DTR protocol, except 
that the Reverse Channel signal (pin 11) is used instead of 
the Data Terminal Ready signal (pin 20).