Varec 8300 series, Installation And Operation Manual, Page: 94 / 150

Tank Gate Interface
84 Installation and Operations Manual
8303 Dual RS-485 Communications Interface Module
If the Radar Tank Gauges are connected to a Saab FCU, then a 8303 Dual RS-485
Communications Interface Module is used to read data, The 8303 Dual RS-485 Communications
Interface Module is automatically detected at startup, and an MSCAN point is automatically
created to manage the scanning task. Chan determines which Channel is used for
communications to the slave device. The Chan parameter must match the channel used to
communicate with the Saab RTG.
8303 TGI software points may begin scanning when the point is created, or when the correct
Channel number is assigned. Which of these events begins the scanning process varies with
each point.
An RTG point is needed for each device connected to the 8303 TGI. The ID must match the unit
address of the Saab RTG. The BaudRate and ComParams values must match the communications
parameters of the Radar Tank Gauge. The communications parameters are set as each RTG point
is processed.
The RTG point works in conjunction with the Modbus Master Protocol Handler (MSCAN). MSCAN
points are automatically created and you only have to set the Chan, BaudRate, ComParams and
ID parameters in order to establish communications with the Saab RTG.
The Mode parameter determines whether the RTG point reads the data from the Saab FCU’s
holding registers. If the Mode is 0x02, then the data is read from the holding registers. The Addr
parameter determines the FCU address and the ID is not used. If the Mode is 0, then the FCU
sends the request to the RTG and sends the response back to the 8303 TGI. The ID is used and
the Addr parameter is ignored. This mode is sometimes referred to as “pass-through’ mode.
Weights & Measures Protection
The RTG point can be sealed when used in a Weights & Measures application. Only certain
parameters can be sealed. These parameters will be shown in blue (CONSTANT parameters)
when unlocked and will be grayed out when locked. To seal the point, set the WMSeal to Enable.
Note that FuelsManager must be active in order to seal or unseal a point.