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Description (see setting description format info here)
| Function: | Selects full-duplex or half-duplex mode for the serial port of the DS (when in the data routing mode) |
| Set (S) command format: | SSIx, where x: 0 (full-duplex), 1 (half-duplex), 2 (auto) |
| Post-initialization value: | 2 (auto) |
| First introduced: | Earlier than "baseline" V3.14/V3.51 |
Details
Serial port of the DS can operate in full-duplex or half-duplex mode. "Full-duplex" and "half-duplex" here refers exclusively to the logical operation of the DS, not to the hardware implementation of the serial port, which depends on the DS model.
The setting only influences the operation of the serial port in the data routing mode. When the serial port is in the serial programming mode it is always using the half-duplex interface- see serial programming for details.
| 1 (half-duplex) | Suitable for RS485 communications. In this mode the RTS line provides direction control and the CTS line is unused. When the Ethernet-to-serial buffer of the DS is empty (nothing to send out through the serial port) the RTS line is HI*. When there is some data to send out the RTS line is LOW* for as long as the data is being output. Such behavior is intended to allow the RTS line to control the direction pin of the RS485 interface ICs and RS232-to-RS485 converters. |
| 2 (auto) | In this mode the DS selects full-duplex or half-duplex mode automatically, depending on the hardware. For Ethernet Modules selection is done by interconnecting or not interconnecting a pair of I/O pins. External Device Servers carry necessary selection circuit internally. Table below details interface selection through "hardware". |
Hardware selection of full-duplex/half-duplex mode on Tibbo Device Servers
When Serial Interface is at 2 (auto) the DS selects full-duplex or half-duplex mode for its serial port basing on "hardware". Table below details hardware-based mode selection.
DS Model
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For full-duplex mode
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For half-duplex mode
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Comments
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EM100
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Leave CTS/SEL and ER/WS unconnected
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Connect CTS/SEL to ER/WS**
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EM120
EM200
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Leave CTS/SEL and SR unconnected
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Connect CTS/SEL to SR**
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DS100
EM100-EV
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Always selected
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These products are based on the EM100; they only support RS232 i/f so CTS/SEL and ER/WS are left unconnected internally
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DS100B
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Depends on jumpers
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This product is based on the EM100; jumpers "decide" whether CTS/SEL and ER/WS are interconnected
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DS203
EM120/EM200-EV
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Always selected
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These products are based on the EM120 or EM200; they only support RS232 i/f so CTS/SEL and SR are left unconnected internally
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* HI and LOW states are described with respect to the serial ports of DS100R, DS100B, DS203. For EM100, EM120, EM200, EM203(A) the signaling is exactly opposite.
** Whether or not these two lines are interconnected is tested once at powerup. Connecting or separating these line during device operation will not cause immediate change of selected interface mode.
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