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參數(shù)資料
| 型號： | LDM422 |
| 廠商： | Electronic Theatre Controls, Inc. |
| 英文描述： | Fully Isolated Limited Distance Modem, RS-232/422 Converter |
| 中文描述： | 完全隔離的距離有限的調(diào)制解調(diào)器，RS-232/422轉(zhuǎn)換器 |
| 文件頁數(shù)： | 3/4頁 |
| 文件大?。?/td> | 158K |
| 代理商： | LDM422 |
20
Notes: (1) For data channels MARK is A negative relative to B. (2) For control lines Assertion
is A positive relative to B. (3) RTS = Request To Send, CTS = Clear To Send, TD =
Transmtted Data, RD = Received Data. (4) Recommended wre sizes are 14AWG to 22AWG.
Belden 8442 or Signal 1172 are typical lowcost, nonshielded, twsted pair cables for use
wth LDM422. (5) Signal return is not required. Cable shield, if used, should be connected
to SIGNAL RTN. (6) For the data rates of the LDM422, termnation resistors are not normally
needed. If desired they may be easily attached to the screwtermnals. Use a 220
resistor
across receiver A' and B' termnals at the extreme ends of the cable.
Figure 2. Field Wiring, LDM to LDM
Unit 1
Unit 2
Function
Function
Terminal
Terminal
12VAC
PWR RTN
(local)
A
B
A’
B’
A
B
A’
B’
RTS
Output
CTS
Input
TD
Output
RD
Input
SIGNAL RTN
SIGNAL RTN
12VAC
PWR RTN
(local)
A’
B’
A
B
A’
B’
A
B
SIGNAL RTN
SIGNAL RTN
1
2
3
4
5
6
7
8
10
11
9
12
1
2
3
4
5
6
1
2
5
6
3
4
10
11
7
8
9
12
7
8
9
10
11
12
Note: Signal return
not required. Shield
connection if used.
specifications for 2400 baud and above by a proportionate amount.
For example, shielded cable wth 50pF/ft (164pF/m) would reduce
the distances by 50%. Recommended wre gauges are #18 to #24
(0.82-0.20mm
2
).
For baud rates of 1200 and below distances are limted by DC voltage
drop. For 2400 baud and above, distances are limted by pulse
distortion. The use of low-capacitance cable can extend the distances
shown. Belden 9182 and 9184 are, respectively, single and dual
twsted-pair cables that are especially designed for high-speed data
communications applications. With these cables the distances can
be extended by 50%. However, the DC-resistance-limted distance
given under 1200 baud may not be exceeded.
Cable capacitance for individually shielded wre pairs is usually given
by manufacturers as capacitance between wres and capacitance from
each wre to the shield. The effective transmssion line capacitance is
approximately the interwre capacitance plus one-half of the wre-to-
shield capacitance.
Installation
Installation of the LDM422 consists of attaching it to its mating 25-pin
connector on the termnal of the host computer either directly or through
a cable. Optional mounting screws and screwjacks are provided.
The DCE/DTE (Data-Communication Equipment/Data Terminal
Equipment) swtch must be set to be complementary to the termnal
or computer port (DCE connects to DTE and DTE to DCE). Since the
LDM422 is a communications device, its normal setting is DCE.
In the event that the host port is not known, the LED indicators may be
used to find the proper swtch setting. The transmt and receive LEDs
wll be off during a “MARK” which is the normal, or standby, condition
when no data is being transmtted. Set the swtch to the position
which allows these LEDs to be off. The field wring as shown in Figure
2 must be correct. It is sometimes useful to tie the RS-422 data
output back to the RS-422 input during initial check-out.
The four other LEDs indicate the status of various control conditions and
wll be on when these functions are asserted. An open circuit to Request
To Send wll be interpreted as assertion, allowng convenient operation
wth equipment not supporting this function. An open circuit on the
Receive Data line of the RS-422 circuits wll be interpreted as a “MARK”.
For 2-wre half-duplex and for 2-wre multi-drop installations, echo
suppression is available by strapping P1 pin 16 to P1 pin 17. Then
RTS asserted enables echo suppression and forces RD (P1 pin 3) to
a "MARK", -V.
Data Termnal Ready, DTR, must be asserted before the LDM422 can
transmt data. This is normally done by the host computer. For situations
where the host equipment does not have the capability of supplying a
DTR signal, RLSD may be used to automatically assert DTR. On the RS-
232 connector P1 of each LDM422, simply connect RLSD pin 8 to DTR
pin 20. This connection is not appropriate for multi-drop installations.
For multi-drop installations the followng points should be considered
(see Figure 3 for multidrop wring connections):
1. If the LDM422 is not powered, it releases the transmt bus so
other RS-422 devices may use the bus.
2. Local equipment connected to the RS-232 connector must not
leave DTR in the asserted state.
3. An open circuit or zero volts on the RS-232 connector pin 20
(DTR) is equivalent to disassertion.
4. DTR should be asserted at least 5.0μs before start bit and
disasserted at end of last stop bit. This disables RS-422 line after
6.0μs mn.
WARNING! Because PWR RTN and RS-232 GND (P1-7) and shield
(P1-1) are common, when powering more than one unit fromthe same
transformer wre all units' 12VAC's together to one side of the secondary
and all PWR RTNs together to the other side of the secondary
}
To
additional
units
(32max)
A B A’ B’ A B A’ B’ A B A’ B’
TD RD TD RD TD RD
Unit 1 Unit 2 Unit 3
Figure 3. LDM422 Multidrop Wiring Connection
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LDM-42257NI | 功能描述:LED 顯示器和配件 LED Display RoHS:否 制造商:Avago Technologies 顯示器類型:7 Segment 數(shù)位數(shù)量:2 字符大小:7.8 mm x 14.22 mm 照明顏色:Red 波長:628 nm 共用管腳:Common Anode 工作電壓:2.05 V 工作電流:20 mA 最大工作溫度:+ 85 C 最小工作溫度:- 35 C 封裝:Tube |
| LDM422-P | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Fully Isolated Limited Distance Modem, RS-232/422 Converter |
| LDM422-PE | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Fully Isolated Limited Distance Modem, RS-232/422 Converter |
| LDM422-PT | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Fully Isolated Limited Distance Modem, RS-232/422 Converter |
| LDM422-S | 制造商:Texas Instruments 功能描述:CONVERTER RS232-RS422 制造商:Texas Instruments 功能描述:CONVERTER, RS232-RS422 制造商:Texas Instruments 功能描述:CONVERTER, RS232-RS422; Convert From:RS-232; Convert To:RS-422; SVHC:No SVHC (19-Dec-2012); Baud Rate Max:19200; External Depth:173mm; External Length / Height:26mm; External Width:56mm; Operating Distance:11265m; Operating |
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