Yokogawa Touch Screen GP20 - Manual (Page 14)

1-8
IM 04L51B01-17EN
Serial interface converter
The recommended converter is given below.
SYSMEX RA CO.,LTD./MODEL RC-770X, LINE EYE/SI-30FA, YOKOGAWA/ML2
Some converters not recommended by Yokogawa have FG and SG pins that are
not isolated. In this case, do not follow the diagram on the previous page (do not
connect anything to the FG and SG pins). Especially in the case of long distance
communications, the potential difference that appears may damage the GX/GP or
cause communication errors. For converters that do not have the SG pin, they can be
used without using the signal ground. For details, see the manual that comes with the
converter.
On some non-recommended converters, the signal polarity may be reversed (A/B or +/-
indication). In this case, reverse the connection.
For a two-wire system, the host device must control the transmission driver of the converter
in order to prevent collisions of transmit and received data. When using the recommended
converter, the driver is controlled using the RS (RTS) signal on the RS-232.
When instruments that support only the RS-422 interface exist in the system
When using the four-wire system, up to 32 GX/GPs can be connected to a single host
device. However, this may not be true if instruments that support only the RS-422 interface
exist in the system.
When YOKOGAWA’s recorders that support only the RS-422 interface exist in
the system
The maximum number of connection is 16. Some of YOKOGAWA’s conventional recorders
(HR2400 and µR, for example) only support the RS-422 driver. In this case, only up to 16
units can be connected.
Note
In the RS-422 standard, 10 is the maximum number of connections that are allowed on one port
(for a four-wire system).
Terminator
When using a multidrop connection (including a point-to-point connection), connect a
terminator to the GX/GP if the GX/GP is connected to the end of the chain. Do not connect
a terminator to a GX/GP in the middle of the chain. In addition, turn ON the terminator on
the host device (see the manual of the host device). If a converter is being used, turn ON its
terminator. The recommended converter is a type that has a built-in terminator.
Select the appropriate terminator (120 Ω), indicated in the figure, according to the
characteristic impedance of the line, the installation conditions of the instruments, and so on.
1.2 Operations over the Serial Interface