NI SCXI-1125電壓輸出模塊,SCXI-1125配置手冊
EIA-232-D標準是最常見(jiàn)的終端/計算機和終端/調制解調器接口，但尚未完全理解。
這可能是因為并不是所有的線(xiàn)都被清楚地定義，而且許多用戶(hù)認為沒(méi)有必要在他們的應用。設計師通常只考慮自己的設備，但最先進(jìn)的技術(shù)是計算機對計算機或計算機對模型操作。系統應易于連接到任何其他系統系統EIA-232-D標準最初由貝爾公司開(kāi)發(fā)通過(guò)調制解調器連接終端的系統。多次握手為此目的包括了線(xiàn)路。
NI SCXI-1125電壓輸出模塊雖然握手是在許多應用中沒(méi)有必要，線(xiàn)路本身仍然是一部分因為它們便于故障排除。表E-1列出了標準EIA-232-D互連。到正確解釋這些信息，記住EIA-232-D是用于將終端連接到調制解調器。當計算機在沒(méi)有調制解調器的情況下相互連接，其中一個(gè)必須配置為終端（數據終端設備：DTE）和其他作為調制解調器（數據電路終端設備：DCE）。自從計算機通常配置為與終端一起工作在大多數情況下被配置為調制解調器。
對于高電平，信號電平必須介于+3和+15伏之間，并且低電平在-3到-15伏之間。并聯(lián)連接裝置
可能產(chǎn)生超出范圍的電壓，與EIA-232-D相反規范。有幾個(gè)級別的一致性可能適用于典型EIA-232-D互連。最低限度要求是兩條數據線(xiàn)和一個(gè)接地。完整的EIA-232-D的實(shí)施需要12條線(xiàn)路；它可容納：? 自動(dòng)撥號? 自動(dòng)應答? 同步傳輸信號自適應
經(jīng)常實(shí)現的一組握手信號是RTS和CT。在許多系統中使用電流互感器來(lái)抑制傳輸，信號高。在調制解調器應用程序中，RTS被逆轉150微秒后返回為CT。RTS可編程在某些系統中，使用較舊的202型調制解調器（一半雙面打?。?。在某些系統中，電流互感器用于為以下各項提供流量控制：避免緩沖區溢出。如果使用調制解調器，這是不可能的。它是通常需要通過(guò)將CT連接到RTS或一些+12伏電源，如圖E-1所示的電阻器。電流互感器也經(jīng)?？缃又罬C1488門(mén)，該門(mén)具有
輸入接地（為此提供柵極）。
The EIA-232-D standard is the most common terminal/computer
and terminal/modem interface, and yet it is not fully understood.
This may be because not all the lines are clearly defined, and many
users do not see the need to follow the standard in their
applications. Often designers think only of their own equipment,
but the state of the art is computer-to-computer or computer-tomodem operation. A system should easily connect to any other
system.
The EIA-232-D standard was originally developed by the Bell
System to connect terminals via modems. Several handshaking
lines were included for that purpose. Although handshaking is
unnecessary in many applications, the lines themselves remain part
of many designs because they facilitate troubleshooting.
Table E-1 lists the standard EIA-232-D interconnections. To
interpret this information correctly, remember that EIA-232-D was
intended to connect a terminal to a modem. When computers are
connected to each other without modems, one of them must be
configured as a terminal (data terminal equipment: DTE) and the
other as a modem (data circuit-terminating equipment: DCE). Since
computers are normally configured to work with terminals, they
are said to be configured as a modem in most cases.
Signal levels must lie between +3 and +15 volts for a high level, and
between -3 and -15 volts for a low level. Connecting units in parallel
may produce out-of-range voltages and is contrary to EIA-232-D
specifications.There are several levels of conformance that may be appropriate for
typical EIA-232-D interconnections. The bare minimum
requirement is the two data lines and a ground. The full
implementation of EIA-232-D requires 12 lines; it accommodates:
? Automatic dialing
? Automatic answering
? Synchronous transmission Signal Adaptations
One set of handshaking signals frequently implemented are RTS
and CTS. CTS is used in many systems to inhibit transmission until
the signal is high. In the modem application, RTS is turned around
and returned as CTS after 150 microseconds. RTS is programmable
in some systems to work with the older type 202 modem (half
duplex). CTS is used in some systems to provide flow control to
avoid buffer overflow. This is not possible if modems are used. It is
usually necessary to make CTS high by connecting it to RTS or to
some source of +12 volts such as the resistors shown in Figure E-1.
CTS is also frequently jumpered to an MC1488 gate which has its
inputs grounded (the gate is provided for this purpose).
