IBM Infoprint 6500-v05, Maintenance Manual

Page: 174 / 544

Communication Problems
174
Device Handshaking
Handshaking is the exchange of signals between the host computer and the printer to indicate the status of the data being
transferred. In serial data transfer, the printer uses both hardware and software handshaking and transmits both forms
simultaneously when the input buffer is full.
The printer can be used with either serial or parallel host interfaces. Parallel interfaces are usually straightforward, with no
special settings required. Serial interfaces, however, have a variety of possible communication parameter settings.
There are two methods of handshaking:
•
Hardware Handshaking
This is an electrical signal controlled by the logic state on pin 20 of the serial interface connector J2 at the back of the
printer. The signal goes high when the printer is ready to receive data. The signal goes low when the printer is in the busy
state, which indicates that the input buffer is full and can no longer receive data.
•
Software Handshaking
XON and XOFF are software signals that control serial data flow between the printer and the host system. When the printer
input buffer is full, the printer transmits the XOFF (CTRL S) character, which signals the host to stop sending data. When
space becomes available in the input buffer, the printer sends the XON (CTRL Q) character, which tells the host that the
printer is ready to receive more data.
The Printer Interface
The printer will not function properly if an incorrectly wired interface cable or the wrong interface cable is installed.
Cannot access the printer through
PMU over an Ethernet Interface
(continued from previous page) ethernet 12. Press STOP to exit the menu and put the printer in the NOT
READY state.
13. Power off the printer, wait a few seconds, then power on the
printer to activate the new diagnostic port. The PMU will now
establish a connection with the Ethernet Interface.
Host cannot communicate with
6500 printer when hooked up to
TCP/IP to AS/400 with the Ethernet
NIC installed ethernet Refer to the appropriate Ethernet Interface User’s Manual.
Table 4. Common Communications Problems
Problem Interface Common Causes