FarSync Drivers | ![]() |
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V.35 transmit and receive clocks are output on the Y-AA and V-X V.35 connector pins.
The degree of support for internal clocking varies by adapter type and is as shown below:
Adapter Type | Transmit Clock (Y-AA) | Receive Clock (V-X) |
FarSync T2P | N | N |
FarSync T4P | N | N |
FarSync T1U | N | N |
FarSync T2U | N | N |
FarSync T2Ue | N | N |
FarSync T4U (< REV 0.3) | N | N |
FarSync T4U (>= REV 0.3) | Y | N |
FarSync T4U+Async (>= REV 0.3) | Y | N |
FarSync T4Ue | Y | N |
FarSync T4Ue+Async | Y | N |
FarSync T4E | Y | Y |
FarSync T4E+ | Y | Y |
FarSync M1P | Y | N |
FarSync Flex | Y | Y |
Note: some special cable types allow a port to be run in X.21 mode but present the signals on a V.35 connector, this can overcome the limitation where V.35 internal clocking is not provided. For example, a UX35C cable converts between HD26-M (X.21) and MRAC34-F (V.35) and presents a DCE-configured interface. Click here for more details on the UX35C cable.
The Interface Types supported are dependent on the adapter type as shown below:
Interface Type |
M1P |
T2P |
T4P |
T1U |
T2U |
T4U |
T4U+Async |
T4E |
T4E+ |
T2Ue |
T4Ue |
T4Ue+Async |
Flex |
RS232 |
Y |
Y |
Y |
Y |
Y |
Y |
Y |
Y |
Y |
Y |
Y |
Y |
Y |
X.21 |
Y |
Y |
Y |
Y |
Y |
Y |
Y |
Y |
Y |
Y |
Y |
Y |
Y |
V.35 |
Y |
Y |
Y |
Y |
Y |
Y |
Y |
Y |
Y |
Y |
Y |
Y |
Y |
X.21D |
N |
N |
N |
Y |
Y |
Y |
Y |
N |
N |
Y |
Y |
Y |
N |
RS530/449 |
N* |
N |
N |
N* |
N* |
N* |
N* |
Y |
Y |
N* |
N* |
N* |
Y |
RS422 signal levels |
Y |
Y |
Y |
Y |
Y |
Y |
Y |
Y |
Y |
Y |
Y |
Y |
Y |
RS485 |
N |
N |
N |
N |
N |
N |
N |
N |
Y |
N |
N |
N |
Y |
* these products can support a subset of the RS530 interface when used with special cables, e.g. the U530 cable for TxU(e).
X.21 interfaces normally provide a Signal Element Timing function (clock) to synchronize data transfer between DTE and DCE. When running at high speed or with long cables, use of a single clock can present problems. This is because the round-trip delay for the clock from DCE to DTE plus the data from DTE to DCE becomes significant compared to the period of the clock. The preferred solution to this problem, which is available on all adapters, is to use the Invert Rx Clock feature.
An alternate approach, available on some adapters, is to use X.21 Dual Clocking. In this mode clock is sent with the data in each direction, so there is no longer a problem with the round-trip delay. In order to use this feature the X.21 Indicate signal has to be relinquished for use as the second clock; the second clock is always an input.
In order to use Dual Clocking mode when connecting a pair of FarSync devices together, a special X.21 Dual null-modem cable is required. This special null-modem cable differs from the standard one in that it requires Sa-Ia and Sb-Ib connections in each direction. Each end of the link needs to be configured for Internal Clocking as well as X21D Interface Mode.
FM0, FM1 NRZI and Manchester encoding schemes allow clocking information to be embedded in the transmitted serial bit stream. This eliminates the requirement for a separate clock to be provided with the data, as the clock can be recovered from the encoded data.
FM0, FM1 and NRZI encoding schemes are only available on the FarSync Flex and M1P; FM0 is also known as Bi-Phase Space and FM1 as Bi-Phase Mark. Manchester encoding scheme is only available on the T4E+; Manchester is also known as Phase Encoding.
When the FarSync M1P or Flex is running in FM0, FM1 or NRZI mode a limited range rates above 512kbps are supported these are: 768K and 1536K. The FarSync T4E+ is capable of sending and receiving Manchester coded data at up to 10Mbps.
When connecting two such FarSync products together, there are two ways of configuring the clock.
The first method (recommended) sets one end internal and the other external. When running in FM0, FM1, NRZI or Manchester modes the internal end runs from the adapters local oscillator, the external end runs in a slave clocking mode where the recovered received clock is used to transmit data back to the originating device. This ensures all data is timed to the one clock source.
An alternate method of configuring the clocks is to select internal clocking at both ends. In this mode the internal oscillator of each adapter is used to drive the transmitter, with the receiver phase-locked-loop recovering the clock from the data in each case. When running in this mode there will be some small difference in the data rates in each direction due to local oscillator tolerances.
Although some clocking information is included in the NRZI bitstream, it may be inadequate to allow for reliable clock recovery. For this reason an optional separate one times clock can be provided with the NRZI encoded data, for improved reliability.
Whether Asynchronous Data is supported is dependent on the adapter type as shown below:
M1P | T2P | T4P | T1U | T2U | T4U | T4U+Async | T4E | T4E+ | T2Ue | T4Ue | T4Ue+Async | Flex | |
Asynchronous Data |
N |
N |
N |
N |
N |
N |
Y |
Y |
Y |
N |
N |
Y |
N* |
*Flex hardware is asynchronous capable, a later release of the Firmware will support this, contact FarSite for details.
The UCX35C cable is useful in V.35 applications where the
FarSync adapter is required to source
clocking, but does not fully support the generation of clocking. The UX35C
achieves this by
running the adapter in X.21 mode (which does support generation of clocking) and
converting this
to a V.35 (DCE configured) interface.
The UX35C cable passes data and clocks straight through but loops control
signals at the HD26-M
(X.21) and MRAC34-F (V.35) connectors. Control is looped to Indicate on the X.21
side; RTS is
looped to CTS and DTR is looped to DCD and DSR on the V.35 side. The single X.21
clock drives
both transmit and receive clock to the V.35 interface.
Products such as T2P, T4P, T1U, T2U and T4U can use the UX35C cable; the cable
attaches directly
to a T1U or T2U, connects to a T2P via a MTU2 cable and connects to a T4P or T4U
via a MTU4 cable.
The UX35C cable cannot be used with the M1P.
FarSync T4E, T4E+ and Flex do not require the UX35C as they fully support internal
V.35 clocking.
The U530 cable is useful in applications where a FarSync adapter that does not natively support RS530 needs to be connected to a RS530 system. The U530 achieves this by running the adapter in X.21 mode and converting this to a DB25 RS530 (DTE configured) interface.
The U530 provides balanced TxD, RxD, RTS, CTS & TxC. Since only a single clock is provided on the interface, the attached device must guarantee phase and frequency locked transmit and receive clock.
Products such as T2P, T4P, T1U, T2U, T4U, T2Ue and T4Ue can use the U530 cable; the cable attaches directly to a T1U, T2U or T2Ue, connects to a T2P via a MTU2 cable and connects to a T4P, T4U or T4Ue via a MTU4 cable.
The U530 cable cannot be used with the M1P. For M1P, use a
P530 or Q530 cable instead.
FarSync T4E, T4E+ and Flex do not require the U530 as they fully support RS530.
The Internal Clock Rates supported are dependent on the adapter type as shown below:
Clock rate | T2P | T4P | T1U | T2U | T4U | T4Ue |
9600 | Y | Y | Y | Y | Y | Y |
19200 | Y | Y | Y | Y | Y | Y |
38400 | Y | Y | Y | Y | Y | Y |
76800 | Y | Y | Y | Y | Y | Y |
153600 | Y | N | N | N | N | N |
307200 | Y | N | N | N | N | N |
614400 | Y | N | N | N | N | N |
64000 | Y | Y | N | Y | Y | Y |
128000 | Y | Y | N | Y | Y | Y |
256000 | Y | Y | N | Y | Y | Y |
512000 | Y | Y | N | Y | Y | Y |
1024000 | Y | Y | N | Y | Y | Y |
2048000 | Y | Y | N | Y | Y | Y |
4096000 | Y | Y | N | Y | Y | Y |
8192000 | Y | Y | N | Y | Y | Y |
T2Ue, T4E and T4E+ support a large number of Clock Rates, supported rates vary according to Slave/Master configuration:
T2Ue/T4E/T4E+ Clock Rates (Master) |
300, 600,
1200, 2400, 4800,
7200, 8000, 9600, |
T4E/T4E+ Clock Rates (Slave) |
32000, 38400, 57600, 64000, 128000, 256000, 512000, 1024000, 2048000, 4096000, 8192000. |
Note: Listed rates are those supported by latest driver/firmware, older versions support a subset of these.
FarSync Flex/M1P supports the following Clock Rates:
FarSync Flex/M1P Clock Rates (Synchronous) |
15,
25, 30, 50,
60, 75, 100,
120, |
Note: Listed rates are those supported by
latest driver/firmware, older versions support a subset of these. Note
also
that the M1P is not supported on Linux.
Note: The FarSync Flex may not operate reliably at speeds
greater than 1024000 on USB 1.1 interfaces.
Please use USB 2.0 interfaces where possible.
The FarSync drivers can sustain line rates of up to:
support@farsite.com - last updated Wednesday, 17 February 2010
Copyright 2001-2010 FarSite Communications Ltd. |
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