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TTL Questions |
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What are the
differences between industrial and commercial-grade converters?
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Just as there are many differences
between industrial- and commercial-grade computers, the industrial-
and commercial-grade converters differ in many ways, such as the
level of circuit protection, temperature range and noise tolerance.
Most importantly, true industrial-grade converters require rugged
components and reliability-engineering designs to withstand heat,
vibration, shock and other environmental factors, therefore, they
are much more durable
than commercial-grade
converters. Industrial-grade converters are designed to interface
with mission-critical equipment, such as computers, PLC, SCADA and HMI - whether in the field, server room, factory, control room, or
fire command center. Visit
the wikipedia's pages for more information on:
Temperature classifications and
Reliability engineering |
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2. |
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RS232: What is
DTE/DCE? How do I know my RS232 device is a DTE or a DCE?
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DTE
stands for Data Terminal Equipment, a PC is a DTE. DCE stands for
Data Communication Equipment, a Modem is a DCE.
DTE normally comes with a Male Connector, while DCE comes with a
Female Connector, but that is not always the case. Use the guide
below as a simple way to confirm:
Measure Pin 3 and Pin 5 (DB9
Connector) with a multi-meter. If you get a voltage of -3V to -15V,
it is a DTE device. If the voltage is on Pin 2, then it is a DCE
device. Note: The result for the DB-25 Connector is reversed, and
Ground for the DB-25 is on Pin 7.
To learn more about
RS232, check out:
RS232 basics: Three easy steps to understand and control your RS232
devices |
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RS232: What are
Handshake Lines?
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Handshake Lines are used to control the
direction of data flow between DTE and DCE. They are:
RTS (Request to Send) - Asserted by DTE to prepare DCE to receive
data.
CTS (Clear to Send) - RTS Acknowledgment by DCE to allow DTE to
transmit.
DTR (Data Terminal Ready) - Asserted by DTE to indicate that it is
ready to be connected.
DSR (Data Set Ready) - Indicates an active connection by DCE.
DCD (Data Carrier Ready) - Used by modem when a connection has been
established with remote equipment.
RI (Ring Indicator) - Used by the modem to indicate a ring signal from
telephone line. |
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RS232: Do I need to use
handshake lines to control the data direction?
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This is not necessary. The converters
come with the Auto-Turnaround feature, the RS485 transceiver circuit
will change the data direction automatically upon sensing a "start
bit" (a logic high "Mark" to low "Space" transition) from its TTL
data transmit line (TxD). |
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RS232: My control
software requires handshake lines to be tied together (e.g. DTR &
DCR, RTS & CTS). Can I still use your converters?
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Yes, to satisfy the requirements of some
software, the following handshake lines are tied together in the
converters.
- Pin 1 (DCD) is connected to Pin 4 (DTR) and Pin 6 (DCR).
- Pin 7 (RTS) is connected to Pin 8 (CTS).
Note: Above pin assignments are for DTE devices. |
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6: |
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RS232/TTL Distances:
What are the maximum distances?
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TTL signal has a distance limitation of
ten (10) feet (about 3m), while RS232 can go up to fifty (50) feet
(about 15m). |
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7: |
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How do I extend the
TTL distance?
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The TTL signal has a distance limitation
of 10 feet (about 3 m), while the RS485/RS422 can go up to 4000 feet
(1200 m). Since TTL is a full-duplex communication, we recommend to
use our full-duplex RS422/TTL converter (Model:
TTL-485_422-2) to extend
the 5V TTL distance to up to 4000 feet (1200 m). |
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8: |
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How
many serial devices can I connect with the RS485/RS422 to TTL
converter?
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You can connect a maximum of 128 serial
devices on RS485/RS422 side. However, this depends a great deal on a
few factors such as the RS485/RS422 devices connected to the
converter, data baud rate, cable distance, etc. |
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9: |
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RS485/RS422
Termination (120-Ohm): Why is it important and when to use it?
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RS485/RS422 network is normally used over a long distance and in
an electrically noisy environment, noises, reflections, and data
errors might occur if there is no termination on the RS485/RS422
buses. Both ends of the transmission
lines should be terminated to reduce noises and reflections that can
cause data errors. There are several methods of terminating
data lines, and we recommend parallel termination. Instead of using
pull-up or pull-down resistors, the parallel 120-Ohm end-of-line
terminators provide a hassle-free and effective way of termination.
However, since the Terminator will increase the load on the data
circuit, we recommend to turn ON the Terminator only when the
distance exceeds 660 feet (200m).
Note: Unlike other converters on the market that require external
resistors or simply have them built-in permanently without concern
for the heavy DC loading problem, our built-in 120 Ohm terminator
can be easily turned ON or OFF through a simple jumper setting. |
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10: |
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How do I perform a
Loopback Test for my RS232/TTL converter?
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Performing a Loopback Test is easy with
our 232Analyzer software.
Simply
connect
TX (TTL Out) to RX (TTL In), and then send commands from the
232Analyzer software. You should get an echo of the commands sent.
By performing a simple Loopback test like this, you can test both
the Transmitter and Receiver of the RS232/TTL converter. This is
very helpful when you are in doubt about the performance of your
converters or cables. |
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Click
here
to download a FREE copy of 232Analyzer software. |
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11: |
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How do I perform a
Loopback Test for my RS485/TTL converter?
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Performing a Loopback Test is easy
with our 232Analyzer
software. Simply connect two RS485/TTL converters to your PC's
COM ports (if your PC does not have enough COM ports, you may use
USB to RS232 converters or cables). Run two instances of 232Analyzer
software on your PC. When you send commands (i.e. "CommFront" in
ASCII format) from one COM port, you should receive the same
commands on the other, and vice versa. By performing a simple
loopback test like this, you can test both the transmitter and
receiver of the converter. This is very helpful when you are in
doubt about the performance of your converters or cables.
Click
here
to download a FREE copy of 232Analyzer software. |
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12: |
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How do I perform a
Loopback Test for my RS422/TTL converter?
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Performing a Loopback Test is easy with
our 232Analyzer software.
Simply connect your PC's RS422 port to the RS422 side and short TX
and RX on the TTL side,
and then
send commands from the 232Analyzer software. You should get an echo
of the commands sent. By performing a simple Loopback test like
this, you can test both the Transmitter and Receiver of the
RS422/TTL converter. This is very helpful when you are in doubt
about the performance of your converters or cables.
Click
here
to download a FREE copy of 232Analyzer software. |
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