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Date 04/07/2018

By Deltayutyuq

Subject Ошибка частотника насоса

chip. 93 Chapter 6 RS-485 TRANSCEIVER Figure 6-9: This half-duplex RS-485 network has a single data path. All nodes must also share a gorund connection, typically via a ground wire in the network cable.. 94 Inside RS-485 RS-485 DIFFERENTIAL PA I R MAX233 R S- 232 INTERFACE Figure 6-10: This circuit converts between RS-232 and TTL, and between TTL and RS-485. A single-chip solution is the MAX3162E, which contains two RS-232 drivers, two RS-232 receivers, and an independent RS-485 transceiver. If you’re designing a circuit that might use either interface, the MAX3160E can interface 5V logic to either RS-232 or RS-485 as selected by the Mode Functionality input pin. Full Duplex Sometimes when you have two devices with different interfaces, all you want is to link them as cheaply and simply as possible. Over short distances, you can connect a full-duplex RS-485 or RS-422 interface to RS-232 with a few inexpensive components. Figure 6-11 shows a connection between an RS-232 port and an RS-485 port. RS-485’s B output connects to RS-232’s RX input. Referenced to signal ground, the B output is near 0V for a logic 1 and near +5V for a logic 0. As explained in Chapter 4, these voltages don’t meet RS-232’s minimum specification, but RS-232 receivers typically use 5V TTL thresholds. RS-485’s A output is unused and left open. In the other direction, a voltage divider ensures that the differential input voltage doesn’t exceed RS-485’s maximum of ±6V The receiver’s A input is tied to ground. The B input sees about 1/3 of the transmitted RS-232 voltage. If the 95 Chapter 6 Figure 6-11: Use this circuit for a short link between a device with an RS-485 interface and one with an RS-232 interface. RS-232’s TX is ±15V, the RS-485 receiver’s input sees a voltage of about ±5V. If the RS-232’s TX is just ±5V, the RS-485 receiver’s input sees a differential voltage of about ±1.6V, which is well above the minimum requirement of ±0.2V. This interface requires a full-duplex RS-485 or RS-422 in prom-electric.ru

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