This unit converts unbalanced, full-duplex RS-232 signals to balanced, full or half-duplex RS-422 or RS-485 signals. RS-485 is an enhanced version of the RS-422 Standard. It allows multiple drivers and receivers on a two-wire or four-wire system.
The RS-232 port, configured as a DCE port, has a female DB25 connector with pins 2 (TD input), 3 (RD output), and 7 (Signal Ground) supported. Pins 4 (RTS) and 5 (CTS) are tied together, and pins 6 (DSR), 8 (CD), and 20 (DTR) are also tied together. Pins 1 (Frame Ground) and 7 (Signal Ground) are connected straight through to the RS-485 terminal blocks.
The RS-485 terminal blocks support Transmit Data (A-) and (B+), Receive Data (A-) and (B+), Frame Ground, Signal Ground, and +12 VDC input. This model has two LEDs: a Transmit Data LED to show when the RS-485 driver is enabled and a Receive Data LED showing data appearing at pin 3 of the RS-232 port. These are very useful for determining if data is getting through the converter. Note that the TD LED indicates that the RS-485 driver is enabled. Data must be present on pin 2 of the RS-232 side for data to be transmitted out of the RS-485 side. If no data is present, no data will be transmitted even though the TD LED is illuminated.
There are two different methods to enable the RS-485 driver, either by toggling Request to Send (pin 4) of the RS-232 side, or by automatic sensing of the data on Transmit Data (pin 2) of the RS-232 side. This option is user selectable by setting push-on jumpers located next to the terminal blocks. Removing both sets of jumpers completely can also constantly enable the RS-485 driver and receiver. This makes the unit act like an RS-422 converter.
IC1476A-F-EU, IC1477A-M-EU: 2- or 4-wire, half-or full-duplex operation; I
IC1620A-F, IC1625A-F: 2-wire, half-duplex
Transmitter Control —
IC1476A-F-EU: RTS or data or always on;
IC1477A-M-EU, IC1620A-F, IC1625A-F: Data
IC1476A-F-EU, IC1477A-M-EU: 230 VAC, 50 Hz, external;
IC1620A-F, IC1625A-F: From the interface
Black Box Explains
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