Plotter displays: INPUT BUFFER OVERFLOW message.
Plotter displays: INPUT BUFFER OVERFLOW message.
A. Handshaking is an RS-232C communication protocol used to control data
flow between a host and the plotter based on availability of buffer
space. An overflow would occur if the plotter attempted to receive
data from the host computer while it was still trying to process
previous data, and the plotter had no place to store the incoming data.
B. Improper handshaking can cause the plotter to receive an Input Buffer
Overflow error.
C. Types of Serial Handshaking:
1. Hardware Handshaking (Direct Control):
a. Uses a positive or negative voltage applied to a hardware
line (usually CTS) in the serial cable to start or stop
data flow between the plotter and the computer.
b. Hardware handshaking is referred to Direct Control on the
plotters handshaking menu.
c. It is the most reliable form of handshake.
2. Xon/Xoff Handshaking:
a. A coded response from the plotter to the host computer via
the serial cable data line used to control data flow.
Xon = send more data
Xoff = do not send more data
3. Ack/Nak Handshaking:
a. A coded response from the plotter to the host sent via the
serial cable data line to control data flow between the
plotter and the host computer.
Ack = Data received from host was received
(acknowledged).
Nak = Data received from the host has an error, send the
data again
Ack/Nak is rarely used in today's environment.
D. If the plotter displays an Input Buffer Overflow error, check what the
software is using: Xon/Xoff, hardware, or Ack/Nak handshaking.
1. If connected on a network, the network file server is performing
the handshaking.
2. If using a software spooler (e.g., AutoPlot, Concurrent Plot,
Spool-it), then the spooler is performing the handshaking.
3. If using a Windows-based driver, then Windows is performing the
the handshaking.
4. If plotting directly from AutoCad, the information is readily
available in the AutoCad Plotter Configuration Menu.
5. If unable to determine what handshaking the software application
is using, then contact the software vendor.
6. Whenever possible, use hardware handshake. Other forms of
handshake such as Xon/Xoff can lose data.
7. On a DOS-based system, hardware handshake using DOS I/O is the
best way to ensure a good I/O transmission. If the software
application provides the option for plotting to a file, perform
the following:
a. First issue a DOS MODE command to establish the baud rate,
parity, number of bits, and number of stop bits. The
handshake is always direct control (hardware handshake)
when using DOS.
i. The DOS MODE command format is:
MODE com_port:Baud_rate,Parity,Data_bits,Stop_bits,P
where parity is one of the following: (E = even, O =
odd, N = none)
The last character of the MODE statement (i.e., the
letter P), tells DOS to perform retries.
ii. If using COM port 1 at 9600 baud, No parity, 8 data
bits, and 1 stop bit, issue the following DOS MODE
command at the DOS prompt:
MODE COM1:9600,N,8,1,P
iii. If using COM port 2 at 9600 baud, No parity, 8 data
bits, and 1 stop bit, issue the following DOS MODE
command at the DOS prompt:
MODE COM2:9600,N,8,1,P
b. In the application, select the option for plot to a file.
The file name is to be set to the name of the COM port
being used (e.g., COM1 or COM2).
E. When the software handshake method has been determined, set the plotter
to match. To access the handshaking menu on the plotter, perform the
following:
1. Turn the plotter power on.
2. Load and size the media by pressing the softkey under MANUAL.
The softkeys are the four light colored keys that surround your
plotter's display (Liquid Crystal Display).
3. After the plotter is done sizing the media, press the NEXT key
twice.
4. Select Set-up by pressing the softkey above SET-UP.
5. Select Host by pressing the softkey under HOST.
6. Press the softkey under Handshake.
7. Use either of the bottom soft keys to toggle to Xon/Xoff, direct
control or Ack/Nak.
8. Press the EXIT key three times. The plotter will prompt you to
save this change. Press the softkey for YES.
F. It is possible that data was corrupted on its way from the computer to
the plotter.
1. Try removing networks, spoolers, and/or switch boxes. Directly
connect the computer to the plotter to isolate the problem.
2. If your are using an IBM PC or compatible or a Sun workstation
with an RS232 port:
a. Try a different serial cable (e.g., the cable that connects
your PC to the plotter). The plotter uses a straight-
through, 25-pin female to 25-pin male, serial cable.
(CalComp Serial cable part number is: 11772-0250 25 ft.
serial cable). This is not a proprietary cable. It is
commercially available, sometimes called a MODEM cable. A
NULL-MODEM cable will not work.
b. If your PC has a 9 pin connector, a commercially available
9 to 25 pin adapter is acceptable for performing the
conversion.
3. If you are using a Macintosh:
a. Try a different communications cable. The plotter uses an 8-
pin mini-din Macintosh to 25-pin serial cable (CalComp part
number 16623-0029 12 ft. cable).
4. Eliminate any spoolers, buffers, networks, switch boxes, etc.
Directly connect the plotter to the computer.
5. Try another computer. There may be a loose connection on the I/O
card or an interrupt conflict.
6. If using AutoCAD:
a. If arrowheads are not plotting, set the Pen Optimization
Level to zero (or no optimization). The Pen Optimization
dialog box is located in the AutoCAD Plot Menu if using
versions 12 or 13 of AutoCAD. This usually resolves the
problem. Also, check to see that the pen widths are set to
0.010 in the AutoCAD Pen Assignment menu.