Signal Levels and Bus LoadingDriver

Signal Levels and Bus Loading
Drivers that conform to the 485 standard must be capable of producing a differential voltage with
a magnitude of at least 1.5 V into a load of 54 Ω. Receivers that conform to the 485 standard
must be capable of detecting a differential voltage with a magnitude as low as 200 mV. These
two criteria give a considerable margin for reliably communicating between nodes, even when
significant degradation of the signal occurs across the cable and connectors. For this reason,
1 IEC 61036 Alternating Current Static Watt-Hour Meters for Active Energy (Classes 1 and 2) ), International
Electrotechnical Commission
R T R T
Up to 32
Unit Loads
SLAVE NODE N
SLAVE NODE
N-1
SLAVE NODE 1
MASTER NODE
SN75LBC182
SLLA112A
4 RS-485 for E-Meter Applications
RS-485 is well suited to applications requiring long cables between nodes, such as networking
meters located around an industrial site or a residential community.
The actual differential output from a driver depends on the current it must supply into the load.
Because each receiving node requires some bus current, the total current that an active driver
must supply increases as nodes are added to a bus. The 485 standard defines a unit load (UL)
which can be approximated by a 12-kΩ resistance over the full range of bus voltage (-7 V to
12 V) specified for 485 communication. Standard-compliant drivers can generate the required
output signal with 32 of these unit loads on the bus plus a 120-Ω termination resistor on each
end of the bus. These considerations are reflected in industry standards such as DL/T 645 2 ,
which specifies an interface capable of handling at least 32 loads.
Transceivers such as the SN65HVD12 and the SN65HVD3082E are available with reduced unit
loading, meaning they require less current from the bus. Therefore, a network using these 1/8
unit load transceivers can connect up to 256 nodes without overloading any 485-compliant
driver.

結果 (中文) 1:

信号电平和公共汽车上落符合标准 485 的驱动程序必须能够产生与差动电压震级为至少 1.5 V 到 54 Ω。 接收器符合 485 标准负载必须能够探测差分电压级低至 200 mV。这些两个标准给予相当大的利润率为可靠通信节点之间甚至当在电缆和连接器之间会出现重大退化的信号。为此，1 IEC 61036 交变电流静态电能表的有功电能 （1 和 2 类）），国际电工委员会R T R T达 32成组货件奴隶节点 N奴隶节点N-1从节点 1主节点SN75LBC182SLLA112A4 RS-485 申请电子水表RS-485 非常适合于需要长电缆等网络节点之间的应用程序米位于工业站点或住宅小区周围。从驱动程序实际的差动输出取决于它必须提供到负载的电流。因为每个接收节点需要一些母线电流，总电流，活跃的驱动程序将节点添加到一辆公交车，必须供应增加。485 标准定义了一个单位负载 (UL)这可以由 12 k ω 电阻接近母线电压 (对-V 7 的全部范围内12 V) 指定为 485 通信。符合标准的驱动程序可以生成所需输出信号与这些单位载荷在公车上的加上每个 120 Ω 终端电阻 32总线的一端。这些考虑都反映在行业标准，如 DL/T 645 2它指定接口能够处理至少 32 荷载。如 SN65HVD12 和 SN65HVD3082E 收发器可减少单位加载，意味着他们需要从总线低电流。因此，使用这些 1/8 的网络单位负载收发器可以连接最多 256 个节点没有超载 485 任何兼容驱动程序。

結果 (中文) 3:

信号电平和总线负载符合485标准的驱动程序必须能够产生一个差分电压大小至少为1.5 V到54Ω负荷。符合485标准的接收机必须能够检测的差分电压，低至200。这些两个标准提供了一个相当大的保证金，可靠的节点之间的通信，即使当信号的显着退化发生在电缆和连接器。因为这个原因，1 IEC 61036交流静电电度表的有效能量（等级1和2）），国际电工委员会R T高达32机组负荷从节点n从节点N-1从节点1主节点sn75lbc182slla112a在电表中的应用4 RS-485RS-485是适合需要的节点之间的长电缆的应用，如网络仪表位于工业现场或住宅社区。从一个驱动程序的实际差分输出取决于它必须提供到负载的电流。由于每个接收节点都需要一些总线电流，因此，一个有效的驱动程序的总电流必须提供增加的节点被添加到一个总线。485标准定义了一个单位负载（UL）这可以近似为一个12-kΩ电阻在母线电压的全范围（7 V12伏）指定的485通信。标准兼容的驱动程序可以生成所需的在公共汽车上加120Ω终端电阻每32单位负载的输出信号巴士的尽头。这些考虑反映在行业标准，如/ T 2 645，指定一个能够处理至少32个负载的接口。如sn65hvd12收发器和sn65hvd3082e可降低单位加载，这意味着他们需要较少的电流从总线。因此，一个网络使用这些1 / 8单元负载收发器可以连接到256个节点，不超载任何485兼容司机。