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8

LD485A-HS and LD485A-HS Opto-Isolated

Driver Enabled by Data

The RS-485 driver can also be enabled without requiring an RS-232 control
lead to be asserted. When jumper W15 is placed in the B-C position, the
driver is enabled when data is received on the RS-232 port of the LD485A-HS.
As soon as the first bit of the first character is received at the RS-232 port, the
RS-485 driver is enabled and an internal timer is started. The time begins its
“time out” on a low (0) to high (1) transition of data. When the timer times
out, the RS-485 driver is disabled. Jumper W17 allows this timeout delay to be
set for 0.15, 0.7, 2, 7, or 70 msec.

NOTE

There is a limitation to using this “DATA ENABLES DRIVER” feature. At
data rates above 64 Kbps, the first character in the data stream will be
garbled by the LD485A-HS. If higher data rates are required, transmit a
<break> if possible, or a <nul> character before each message. This will
enable the RS-485 driver, activate the timer, and allow the message to be
transmitted without errors. The receiving device will need to ignore the
first character received.

Driver Constantly Enabled (4 Wire Only)

The RS-485 driver can be constantly enabled by setting jumper W9 to the

ON position.

3.1.6  H

ALF

-D

UPLEX

T

URNAROUND

D

ELAY

When operating in half-duplex mode (jumper W8 in the HALF position),

the LD485A-HS adds a small delay each time it stops transmitting data and

prepares to receive data. This delay allows the RS-485 interface and
transmission line time to stabilize, thus reducing the possibility of garbled
data being received at the end of a message.

The turnaround delays are 0 (W16 in position A), 0.1 msec (W16 in position
B), 1 msec (W16 in position C), 5 msec (W16 in position D), and 35 msec
(W16 in position E).

3.1.7  RS-485 I

NTERFACE

T

ERMINATED OR

U

NTERMINATED

Some distortion on the twisted-pair line may be caused by impedance
mismatch from the different devices connected to the line. To help eliminate
this type of distortion, the RS-485 interface can be terminated with a resistor
network at the receiver input pins (RXA and RXB) via switch S2. When S2 is
placed in the “TERM” position, the resistor network is connected across the
line. When S2 is placed in the “UNTERM” position, no connection to the

Содержание LD485A-HS

Страница 1: ...der Black Box Corporation 1000 Park Drive Lawrence PA 15055 1018 Web site www blackbox com E mail info blackbox com SEPTEMBER 1999 ME837A R2 ME837AE ME837C R2 ME838A R2 ME838AE ME838C R2 BC00702 FA520A R2 LD485A HS LD485A HS Card LD485A HS Opto Isolated LD485A HS Isolated Card LD485A HS OPTO ISOLATED TX RX CD RTS PWR NORMAL DLB RX TX RTS CD DCE DTE LD485A HS TX RX CD RTS PWR NORMAL DLB RX TX RTS C...

Страница 2: ... operated in a commercial environment Operation of this equipment in a residential area is likely to cause interference in which case the user at his own expense will be required to take whatever measures may be necessary to correct the interference Changes or modifications not expressly approved by the party responsible for compliance could void the user s authority to operate the equipment This ...

Страница 3: ...4 3 1 2 Frame Ground Signal Ground 4 3 1 3 Half Full Duplex Operation 5 3 1 4 CTS Delay 7 3 1 5 RS 485 Driver Enable 7 3 1 6 Half Duplex Turnaround Delay 8 3 1 7 RS 485 Interface Terminated or Unterminated 8 3 1 8 Normal Loopback Operation 9 3 1 9 RS 485 Interface Line Biased Fail Safe 9 3 2 DCE Configuration DTE Configuration 10 3 3 Typical Applications 18 Appendix A Pinning 25 ...

Страница 4: ...sparent to data Indicators 5 LEDs TX RX RTS CD and PWR Temperature Operating 32 to 122 F 0 to 50 C Storage 4 to 158 F 20 to 70 C Humidity 0 to 95 relative humidity noncondensing MTBF Approximately 180 000 hours ground benign environment Power PS154 for use with ME837A R2 ME838A R2 Input 120V 60 Hz 20W Output AC 17VCT 0 7A PS154E for use with ME837AE ME838AE Input 230V 50 Hz 20W Output AC 17VCT 750...

Страница 5: ...eration Timeout Delay 0 15 0 7 2 7 or 70 msec for the RS 485 driver enabled by data feature Typical Speed Versus Distance 4 wire point to point 26 AWG twisted pair SPEED DISTANCE 1200 bps 4 miles 6 4 km 2400 bps 3 miles 4 8 km 4800 bps 2 3 miles 3 7 km 9600 bps 1 7 miles 2 7 km 19 200 bps 1 2 miles 1 9 km 38 400 bps 0 9 mile 1 4 km 64 000 bps 0 75 mile 1 2 km 115 Kbps 0 4 mile 0 6 km NOTE Speed an...

Страница 6: ...electrical noise from your factory floor won t affect your office communications and the difference in ground potential between buildings won t damage your sensitive equipment Additional features include a manual loopback test to check the system wiring for both the RS 232 and RS 485 interfaces and transient protection on the RS 485 interface to help prevent damage due to voltage transients on the...

Страница 7: ...3 Apply power PS154 or PS154E depending on which LD485A HS you have See Chapter 1 for more information 3 1 Jumper and Switch Configuration NOTE As you read this section refer to Tables 1 and 2 Table 1 page 11 lists DCE jumper settings and Table 2 page 16 lists DTE jumper settings 3 1 1 DTE DCE CONFIGURATION A DIP shunt is used to select DTE or DCE configuration For the LD485A HS to appear as a DTE...

Страница 8: ...d circulating currents are limited to acceptable levels 3 1 3 HALF FULL DUPLEX OPERATION Jumper W8 selects half duplex or full duplex operation Set W8 to the HALF position for half duplex operation Set W8 to the FULL position for full duplex operation NOTE When the jumper W9 is in the ON position and jumper W15 is in the A B position the RS 485 driver is always turned on to enable transmission of ...

Страница 9: ... W17 DRIVER ENABLE HOLD A 70ms B 7ms C 2ms D 0 7ms E 0 15ms B C A W19 B C A W15 A B RTS CD ENABLED B C DATA ENABLED W9 30 mesc 10 mesc 0 mesc ON A B RTS CTS B C RTS CTS CD W5 A B C W15 W8 A B C A B C D E A B C D E A W16 W8 A B 2 WIRE B C 4 WIRE W16 TURNAROUND A 0ms B 0 1ms C 1ms R49 W7 1 2 3 4 P2 O N O N BIAS TERM XW1A DCE TB1 XW1B DTE W18 A B C J1 T A T B R A R B ...

Страница 10: ...TS will immediately go false If jumper W9 is in the ON position CTS will follow RTS LD485A HS as DTE When the LD485A HS is configured as a DTE device DIP shunt in position XW1B CTS is not supported 3 1 5 RS 485 DRIVER ENABLE The LD485A HS s RS 485 driver can be set to be enabled one of three ways by RS 232 control signals by data or constantly on Driver Enabled by RS 232 Control Leads If your equi...

Страница 11: ...rrors The receiving device will need to ignore the first character received Driver Constantly Enabled 4 Wire Only The RS 485 driver can be constantly enabled by setting jumper W9 to the ON position 3 1 6 HALF DUPLEX TURNAROUND DELAY When operating in half duplex mode jumper W8 in the HALF position the LD485A HS adds a small delay each time it stops transmitting data and prepares to receive data Th...

Страница 12: ...ed as terminated the amount of distortion could increase possibly causing errors in the data being transmitted 3 1 8 NORMAL LOOPBACK OPERATION The Normal Loopback switch S1 is a two position pushbutton switch extending through the front panel The Normal position permits normal operation of the LD485A HS The Loopback position allows data coming into the LD485A HS to be sent back out the same port T...

Страница 13: ...rs and switches see Section 3 1 Figure 2 Simplified Functional Block Diagram DCE Operation RS 232 RECEIVER TD TXA TXB RS 485 DRIVER TX ENABLE RS 232 DRIVER ENABLE RS 485 RECEIVER RD CD DSR ON RX RTS DATA RECEIVED ENABLES RS 485 DRIVER CIRCUIT HALF DUPLEX TURNAROUND DELAY CIRCUIT CARRIER DETECT CIRCUIT CD CTS RXB RXA W17 W15 W8 W16 W9 W5 HALF FULL B C A A B C ON 30 msec 10 msec 0 msec RTS Opto Isol...

Страница 14: ...1 in A position 2 Signal ground connected to frame ground Connected W7 is IN solder your own 100 ohm 1 2 watt resistor in place Not connected W7 is OUT 3 Half or full duplex operation Full duplex W8 in FULL position 4 wire A B Half duplex W8 in HALF position 2 wire B C 4 CTS delay Yes W9 in 0 ms position W9 in 10 ms position W9 in 30 ms position No W9 in ON position no delay CTS follows RTS ...

Страница 15: ...9 in 30 ms position b RS 485 driver enabled by data W15 in B C position and Disable timeout delay W17 msec A 70 B 7 C 2 D 0 7 E 0 15 c RS 485 driver constantly enabled W9 in ON position 6 Half duplex turnaround delay W8 in HALF position and 0 msec turnaround delay W16 in position A 0 1 msec turnaround delay W16 in position B 1 msec turnaround delay W16 in position C 5 msec turnaround delay W16 in ...

Страница 16: ...r unterminated Terminated S2 in TERM position Unterminated S2 in UNTERM position 8 Normal or loopback operation Normal mode S1 in Normal position Loopback mode S1 in Loopback position 9 RS 485 Interface Line Biased Fail S3 Off No line bias Safe Receive S3 On Line biased NOTE If line bias is on the RS 485 CD will ALWAYS be on ...

Страница 17: ...14 LD485A HS and LD485A HS Opto Isolated Figure 3 Line Bias S2 shows the line termination when Term is selected S3 shows line bias when Bias is selected Rx S3 S2 5V S3 Tx ...

Страница 18: ...ition will allow the CD input to enable the RS 485 driver When jumper W9 is in the ON position the CD input has no affect on the RS 485 driver RS 232 RECEIVER RD TXA TXB RS 485 DRIVER TX DTR ON DATA RECEIVED ENABLES RS 485 DRIVER CIRCUIT HALF DUPLEX TURNAROUND DELAY CIRCUIT CD W17 W15 W16 W9 A B ON 30 msec 10 msec 0 msec CD CTS DSR NOT USED NOT USED RX RS 232 DRIVER ENABLE RS 485 RECEIVER TD RTS R...

Страница 19: ...Signal ground connected to frame ground Connected W7 is IN 100 ohm 1 2 watt resistor soldered in place Not connected W7 is OUT 3 Half or full duplex operation Full duplex W8 in FULL position 4 wire A B Half duplex W8 in HALF position 2 wire B C 4 CTS delay CTS not supported 5 Enable RS 485 driver a RS 485 driver enabled by W15 in A B position and RS 232 lead CD W9 in 0 ms position W9 in 10 ms posi...

Страница 20: ... turnaround delay W8 in HALF position and 0 msec turnaround delay W16 in position A 0 1 msec turnaround delay W16 in position B 1 msec turnaround delay W16 in position C 5 msec turnaround delay W16 in position D 35 msec turnaround delay W16 in position E 7 RS 485 interface terminated or unterminated Terminated S2 in TERM position Unterminated S2 in UNTERM position 8 Normal or loopback operation a ...

Страница 21: ...alf duplex connection with both LD485A HSs terminated by setting switch S2 to the TERM position Figure 6 shows a typical point to point 2 wire half duplex connection with both LD485A HSs terminated by setting switch S2 to the TERM position In a 4 wire point to point application each of the drivers on the two LD485A HSs may always be enabled without any adverse effects In a 2 wire point to point or...

Страница 22: ...r Half Duplex Figure 6 Point to Point 2 Wire Half Duplex RS 232 DEVICE 1 TXA TXB RXA RXB RXA RXB TXA TXB RS 232 DEVICE 2 TERMINATED TERMINATED RS 232 DEVICE 1 TXA TXB RXA RXB RXA RXB TXA TXB RS 232 DEVICE 2 TERMINATED TERMINATED LD485 HS LD485 HS LD485 HS LD485 HS ...

Страница 23: ...d by setting switch S2 to the TERM position These devices are the two devices that have the greatest cable length between them not necessarily the devices that are physically located the farthest apart See Figures 7 and 8 A resistor shown in the circuit indicates that the termination resistor has been selected via switch S2 Note that although Figures 7 and 8 show only four LD485A HS devices networ...

Страница 24: ... Full Duplex RS 232 DEVICE 1 TERMINATED UNTERMINATED SUBORDINATE RS 232 DEVICE 2 UNTERMINATED SUBORDINATE RS 232 DEVICE 3 RS 232 DEVICE 4 TERMINATED RXA RXB TXA TXB TXA TXB RXA RXB RXA RXB TXA TXB RXA RXB TXA TXB MASTER MASTER LD485 HS LD485 HS LD485 HS LD485 HS ...

Страница 25: ...re 8 Multipoint 2 Wire Half Duplex RS 232 DEVICE 1 TXA TXB RXA RXB TERMINATED UNTERMINATED RS 232 DEVICE 2 UNTERMINATED RS 232 DEVICE 3 RXA TXB RXA RXB RS 232 DEVICE 4 TERMINATED TXA TXB RXA RXB TXA TXB RXA RXB LD485 HS LD485 HS LD485 HS LD485 HS ...

Страница 26: ...allation procedure follows Figure 9 Installation Procedure for the Multipoint Application in Figure 9 1 Set all the LD485A HSs for DCE operation jumper XW1 in position A 2 Connect a straight through cable from the RS 232 port on each LD485A HS to the RS 232 port on each of the PLCs 3 Set all the LD485A HSs for normal operation switch S1 in the Normal position 4 After a remote station has been addr...

Страница 27: ...ontroller in our example so it would be wise to set the CTS Delay jumper W9 for 10 msec This allows the line to stabilize after a remote PLC becomes active but before it starts to transmit 8 Set jumper W9 on the LD485A HS connected to the industrial controller to the ON position This allows the industrial controller to transmit to the remote PLCs without having to wait for any delay period 9 Set j...

Страница 28: ...CE 3 bb Receive Data Data From DCE 4 CA Request To Send Control To DCE 5 CB Clear To Send Control From DCE 6 CC Data Set Ready Control From DCE 7 AB Signal Ground Ground 8 CF Data Carrier Detect Control From DCE 9 DC Test Voltage 10 DC Test Voltage 11 Unassigned 12 SCF Secondary Data Control From DCE Carrier Detect 13 SCB Secondary Clear Control From DCE To Send Appendix A Pinning ...

Страница 29: ... Data To DCE Data 15 DB Transmit Signal Timing From DCE Element Timing DCE 16 SBB Secondary Receive Data From DCE Data 17 DD Receiver Signal Timing From DCE Element Timing 18 Local Loopback Test To DCE 19 SCA Secondary Request Control To DCE To Send 20 CD Data Terminal Ready Control To DCE 21 CG Signal Quality Control From DCE Detector 22 CE Ring Indicator Control From DCE ...

Страница 30: ...hart Pin Name Description TXA and TXB Data received by the LD485A HS at the RS 232 port is transmitted out of the unit over twisted pair wires via these two outputs The TX LED indicates the state of these two leads When the TXA lead is positive with respect to the TXB lead a zero is being transmitted the TX LED is lit RXA and RXB These are the received data inputs for the RS 485 port The status of...

Страница 31: ...delay CTS inhibited if CD is present when RTS is raised W9 RTS CTS delay The time before the RS 485 driver is enabled and CTS is asserted after RTS is asserted The RS 485 driver is always enabled A 30 msec B 10 msec C 0 msec D ON W17 When W15 is in the B C Data Enabled position this is the time the RS 485 driver remains enabled after a low to high transition on the DATA line to prevent disabling t...

Страница 32: ... 1 msec D 5 msec E 35 msec NOTE If the LD485A is configured Data Enabled W15 position B C and 2 wire W8 position B C then delays from W17 and W16 are cumulative S1 OUT Normal IN Loopback S2 OFF RS 485 Receiver Unterminated ON RS 485 Receiver Terminated S3 OFF Line Bias Off ON Line Bias On The Carrier Detect light will come on Default is 5 volts TB1 4 wire terminal block 1 Rx B 2 Rx A 3 Tx B 4 Tx A...

Страница 33: ...1000 Park Drive Lawrence PA 15055 1018 724 746 5500 Fax 724 746 0746 Copyright 1999 Black Box Corporation All rights reserved ...

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