Tech Serial v1r0c0 PDF
Tech Serial v1r0c0 PDF
Tech Serial v1r0c0 PDF
2002 12 - 06
Table of Contents
1: Introduction
1.1. 1.2. DCE and DTE Devices Synchronous data transfer Asynchronous data transfer
1.3. 2: RS232
2.1. 2.2. 2.3. 2.4.
RS232 on DB9 (9-pin D-type connector) RS232 on DB25 (25-pin D-type connector) RS232 on RJ-45 Signal Description Limitations of RS232
2.5.
3.2. 3.3.
4: Summary Table
5.4. 5.5.
1. Introduction
The purpose of this application note is to attempt to describe the main elements in Serial Communication. This application note attempts to cover enough technical details of RS232, RS422 and RS485.
Description Data carrier detect Receive Data Transmit Data Data terminal ready Signal ground Data set ready Ready to send Clear to send Ring Indicator
Pin Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Signal PG TD RD RTS CTS DSR SG CD + SCD SCS STD TC SRD RS SRS DTR SQD RI DRS XTC
Description Protective ground Transmitted data Received data Request to send Clear to send Data set ready Signal Ground Carrier detect Voltage (testing) Voltage (testing) Secondary CD Secondary CTS Secondary TD Transmit Clock Secondary RD Receiver clock Ready to Send Secondary RTS Data Terminal Ready Signal Quality Detector Ring Indicator Data rate select External Clock
Pin No. 1 2 3 4 5 6 7 8
Notes/Description Data set Ready/ring indicator Data Carrier Detect Data Terminal Ready Signal Ground Receive Data Transmit Data Clear to Send Request to Send
RXD: - This pin carries data from the serial device to the computer
DTR signals: - DTR is used by the computer to signal that it is ready to communicate with the serial device like modem. In other words, DTR indicates to the Dataset (i.e., the modem or DSU/CSU) that the DTE (computer) is ON.
DSR: - Similarly to DTR, Data set ready (DSR) is an indication from the Dataset that it is ON.
DCD: - Data Carrier Detect (DCD) indicates that carrier for the transmit data is ON.
RTS: - This pin is used to request clearance to send data to a modem CTS: - This pin is used by the serial device to acknowledge the computer's RTS Signal. In most situations, RTS and CTS are constantly on throughout the communication session.
communications. The modem or DSU extracts the clock from the data stream and provides a steady clock signal to the DTE. Note that the transmit and receive clock signals do not have to be the same, or even at the same baud rate. CD: - CD stands for Carrier Detect. Carrier Detect is used by a modem to signal that it has a made a connection with another modem, or has detected a carrier tone. In other words, this is used by the modem to signal that a carrier signal has been received from a remote modem.
RI: - RI stands for Ring Indicator. A modem toggles(keystroke) the state of this line when an incoming call rings your phone. In other words, this is used by an auto answer modem to signal the receipt of a telephone ring signal The Carrier Detect (CD) and the Ring Indicator (RI) lines are only available in connections to a modem. Because most modems transmit status information to a PC when either a carrier signal is detected (i.e. when a connection is made to another modem) or when the line is ringing, these two lines are rarely used.
communications. It supports several types of connectors, including DB-9 and DB-37. RS-485 is similar to RS-422 but can support more nodes per line RS485 meets the requirements for a truly multi-point communications network, and the standard specifies up to 32 drivers and 32 receivers on a single (2-wire) bus. With the introduction of "automatic" repeaters and high-impedance drivers / receivers this "limitation" can be extended to hundreds (or even thousands) of nodes on a network. The RS-485 and RS-422 standards have much in common, and are often confused for that reason. RS-485, which specifies bi-directional, half-duplex data transmission, is the only EIA/TIA standard that allows multiple receivers and drivers in "bus" configurations. RS-422, on the other hand, specifies a single, unidirectional driver with multiple receivers.
For example, an Automatic RS232<=>RS485 converter, could be connected to a computer's RS232, full-duplex port, and transform it into an RS485 half-duplex, multi-drop network at distances up to 4000ft. Converters in most instances, pass data through the interface without changing the timing and/or protocol. While the conversion is "transparent" the software must be able to communicate with the expanded network features. An "Automatic Converter" (RS232<=>RS485) will turn on the RS485 transmitter when data is detected on the RS232 port, and revert back into the receive mode after a character has been sent. This avoids timing problems (and software changes) that are difficult to deal with in typical systems. When fullduplex is converted into half-duplex only one device at a time can transmit data. Automatic Converters take care of the timing problems and allow fast communications without software intervention.
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Specifications for RS232, RS423, RS422, and RS485 Specifications RS232 RS423 RS422 RS485
Mode of Operation Allowed no. of Tx and Rx Maximum cable length Maximum data rate Minimum driver output range Maximum driver output range Tx load impedance (Ohms) Rx input sensitivity Rx input voltage range Maximum Rx input resistance (Ohms)
100 kbps / 10 mbps 100 kbps / 10 mbps 100 kbps / 10 mbps 3.6V 6V >=450 200mV 12V 4k min 2V 6V 100 200mV 7V 4k min 1.5V 6V 54 200mV -7V to +12V >=12k
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Sena Product HelloDevice Lite Series HelloDevice Pro Series HelloDevice Super Series POSLink IALink VTS
Supported Serial Interface RS232 via DB9 serial port RS232/422/485 via DB9 serial port RS232/422/485 via DB9 serial port RJ11 serial port RS232/422/485 RS232 via RJ45 connector
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5.3.
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5.4. IALink100
Below picture shows the Pin layout and Pin assignment of the IALink100.
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Pin 1 2 3 4 5 6 7 8
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