Epson GQ-3500 User manual

EPSON
®
Serial Interface
for the
GQ-3500
Printed in Japan
m 88.11-5
Y59099101000

Serial Interface
The serial interface is an option for your CQ-3500 printer. These
pages tell you how to install and use the serial interface.
The GQ-3500 serial interface is actually two interfaces in one. It
can be used as either an RS-232C interface (the factory setting) or an
RS-422 interface, depending on the settings of the jumpers on the circuit
board.
Setting up the Serial Interface
When you receive your serial interface, it is configured as an
RS232C interface, 9600 baud, 8 data bits, no parity, 1 or 2 stop bits,
with the printer ready protocol enabled. This configuration will work
for many applications
To use this configuration with
®
PC computers, use the
following command at the DOS prompt
MODE COM1:9600,N,8,1,P
If you need to change the configuration of the serial interface
follow these steps:
1.
Refer to your computer and software documentation to see what the
requirements are for a serial interface printer.
2. Select the RS-232C or RS-422 interface. The jumpers at Jl and J2
will have to be reconfigured for RS-422. Because RS232C is the
factory setting, the jumpers will not have to be reconfigured if you
choose this interface. For information on the location of Jl and J2
and on how to reconfigure the jumpers for the specific settings
described below, see the Serial Interface Jumpers section.
If you have changed the factory settings and want to reconfigure
the lumpers for RS232C operation, set the jumpers at Jl and J2 as
follows. At Jl, move REV, RD, and SRI to the left.
At J2, all
jumpers should be disconnected.
Serial Interface
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3.
4.
5.
6.
For RS422 operation, set the jumpers at Jl and J2 as follows.
At Jl,
move REV, RD, and SRI to the right. At J2, set all jumpers in the
installed position, except for TR+ and TR-.
Jumpers that were not given a especific setting above do not need to
be changed to select RS-232C or RS-422 operation (although they
may affect how the interface works).
Select a baud rate by setting DIP switches 4-1, 4-2, and 4-3 as
indicated in Table 2.(For more information on setting DIP
switches, see the Serial Interface DIP Switches section of this
chapter.)
Select 7 or 8 data bits by setting DIP switch 4-4 on for 8 bits per
character or off for 7 bits per character. Using 8 bits per character
is usually best.If you selected 7 data bits, select even, odd, or no
parity and set DIP switches 4-5 and 4-6 appropriately.
Select a handshaking protocol.If you are using a commercial
software program, look in the manual to see if it requires a
particular protocol. If not, try the printer ready protocol. Set DIP
switches 5-l through 5-4 appropriately.Note that you can use
more than one protocol at the same time.For additional
information, see the Communications Protocols section.
Customize the interface if you need more control of the serial
interface.Study the functions shown in Table 3 that describe the
jumpers.For example,’ it’s possible to add DSR, CIS, and DCD
control to the interface.
Installing the Interface
Installing the serial interface is easy and doesn’t require any tools.
Just follow these steps:
1. Make sum that the power to the printer is off.
2 Set the DIP switches on the interface card as described in
Appendix C.Use a ballpoint pen or similar object to set the
Switches
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Serial Interface

3.
4.
Configure the jumpers on the serial interface card as described
above.
Remove the parallel interface from the back of the printer by
loosening the two Knobs and pulling its straight out as shown in
Figure 1. Store the parallel in the box that the serial
interface came in
Figure 1. Removing the interface
5. Slide the serial interface into the slot on the back of the printer
until it is flush with the printer case.
6. Tighten two two knobs to secure the interface.
7. Connect the serial cable from your computer to the interface.
Serial Inteface
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The Serial Interface DIP Switches
On the right side of the serial interface are two banks of DIP
switches, as shown in Figure 2. Group 4 is on the left and 5 is on the
right.) switches control many of the of the interface ,as
detailed in Table 1.
settings. You can use a ballpoint pen to change the switch
Because DIP switch groups 1 and 2 are the same for both the
serial and parallel, the DIP switch information in Chapter2
and Appendix C applies to both interfaces
Figure2. The serial interface DIP switches
4Serial Interface

Table 1. Serial interface DIP switches
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Setting the data trader rate
The following table shows the DIP switch settings for the various
possible data transfer (baud) rates
Table2. Baud rate settings
The Serial Interface Jumpers
The following tables describe the functions of the jumpers on the
serialinterface. The main function of these jumpers is to switch
between RS-232 C and RS-422 operation, but some of the jumpers allow
you to customize the interface.
The jumpers are located on the interface card as shown in Figure 3.
Figure3. The serial interface jumpers
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6serial Interface

The jumpers at Jl
The jumpers at J1 are two position jumpers. The small plugs can be
moved from the left two wires to the right two wires to change the
settings. Table 3 describes the functions of the jumpers at Jl. When
delivered from the factory, all jumpers are in the left position.
Table3. Functions of the jumpers at J1
Serial Interface
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The jumpers at J2
Jumpers at J2 are single position jumpers; they can be either
installed or disconnected. To change the settigs of these jumpers you
must put a jumper plug across the two pins. To disconnect a jumper plug,
simply move the plug so that it rests on the left pin only, leaving the
right pin open. (All plugs are in this position when the interface is
delivered from the factory.)
Table. Function so the jumpers
T2
Tl
EL
DM
DM+
SD+
TR+
TR-
Connects DM+ and DM- through a 120 ohm resistor.
Connects RD+ and RD- through a 120 ohm resistor.
Connects RD- to pin 9
Connects RD+topin 10
Connects DM- to pin 23
Connects DM+ to pin 24
Connects SD+topin 12
Connects TR+ to pin 25
Connects TR-to pin 13
Communications Protocols
To achieve the maximum printing speed, the computer should send
characters to the printer faster than the printer can print them. This
ensures that the printer has to stop and wait for more
information. But if you continuously send information to the printer
faster than it can print, sooner or later the printer’s buffer will
overflow and information will be lost. A communications protocol keeps
the computer from sending more information than the printer can
handle. *
The GQ-35CN7's serial interface can use three different kinds of
communications protocols These are described in detail below.
The ETX/ACK protocol
The ETX/ACK protocol uses a special pair of control codes, ETX
(ASCII 3) and ACK (ASCII 6). The system is very simple: whenever
the GQ-3500 gets an ETX out of its input buffer it sends an ACK back to
the computer. When the computer receives the ACK it knows it is safe
to send more information to the printer without fear of overflowing the
buffer.
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Serial Interface

The GQ-3500 has a buffer that will hold up to 102 characters,
including the ETX code at the end of the group. The computer can
send the first group of characters and then stop until the first ACK is
received. From then on,every time an ACK is received, another
group of characters can be sent.
DlP switch 5-2 controls ETX/ACK protocol. If DIP switch 5-2
iS Off, the GQ-35OO is ignored the ETX code.
The DCl/DC3 or XON/XOFF protocol
The DC1/DC3 protocol also uses a special pair of control codes,
DCl (AscII 17 decimal, also knwon as XON) and DC3 ( ASCII 19)
decimal, also known as XOFF) This communications protocol is
selected by turning DIP switch 5-1 on.
In this protocol the printer sends a DC3 to the computer to suspend
data entry under the following conditions
1. when the input buffer becomes nearly full (within 128 bytes)
2 When the printer goes offline (by pressing the ONLlNE button)
3. When the printer runs out of paper
4. When the printer runs out of toner
5. When an errror is detected.
when the computer receives the DC3 signal it must stop within
128 characters) sending information until the printer sends a DCl signal
to say that there is more room in the buffer. The printer sends the DCl
signal when the buffer has room for 255 characters
If DIP switch 5-4 is on, the printer will send an additional DC3
after each additional character it receives after it sends the first DC3.
This is called the multiple XOFF function.
The printer ready protocol
The printer ready protocol is a hardware protocol because it uses
one of the wires in cable connecting the computer and printer to tell
the computer where , the printer is ready to accept information. This
communications potocol is selected by turning DIP switch 5-3 on.
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