请问各位大侠啊，想用256个SP3080E的485芯片同时并联到一条总线上，失效保护电路还需要吗？
失效保护：
当 RS-485 接收器输入端电压介于-200mV~+200mV 时 ，输出处于不确定状态即 如果半工结构 RS-485 收发器的差动输入电压为0V 而线上又无其它驱动器使能或由于连线不好导致输出开路 则该接收器既可能输出逻辑 1 也可能输出 0 而且其几率相同，为了保证在上述错误情况下输出一个确定值 当今大多数 RS-485 收发器都需要接失效保护电阻， 其中在线 A 接一上拉电阻 在线 B 接一下拉电阻 。
而我看的SP3080E的英文资料是这样写的：
Ordinary RS485 differential receivers will be in
an indeterminate state whenever A - B is less
than ±200mV. This situation can occur when-
ever the data bus is not being actively driven.
The Advanced Failsafe feature of the SP3080E
family guarantees a logic-high receiver output
if the receiver’s differential inputs are shorted,
open-circuit, or if they are shunted by a termi-
nation resistor. |
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