If the SCADAPack Modbus points are configured to use different Retrieval Intervals, the SCADAPack Modbus driver will poll each register individually according to the point's Retrieval Interval. If the SCADAPack Modbus driver had to poll registers 30001, 30003, and 30050, it would poll 3003 together and poll register 30050 separately as the 'gap' between 3000 is greater than 4 registers. So, if the SCADAPack Modbus driver is to poll registers 30001, 30003, and 30004, it will poll them at the same time rather than individually as the 'gap' is less than 4 registers.
For this reason, the SCADAPack Modbus driver allows a maximum 'gap' of 4 registers or 40 coils depending on the type of data being polled. When the SCADAPack Modbus driver is required to poll sequential registers, it is more efficient to poll the entire range rather than poll each individual register. With the SCADAPack Modbus driver, you only need to configure a single controller). For example, to poll registers 30003, 30004, 30009, you would need to configure 2 Modbus Scanners: 1 scanner for the sequential registers, 3004, and another scanner for register 30009. (Note that this can also be achieved with the simple Modbus driver, but it involves extra configuration work as you need to create and configure separate Modbus Scanners for each non-sequential register. For example, the SCADAPack Modbus driver can poll registers 3000 without polling registers 30002, 30003, 30004 and so on. This means that it can poll individual registers and does not have to poll all registers in a range. Unlike the simple Modbus driver, the SCADAPack Modbus driver dynamically creates the start register for the poll and the amount of data to poll, based on the configuration settings of the point. These configuration settings define which registers are polled and how often they are polled. The address is defined the point configuration, along with an association with a Retrieval Interval (the time scales for the Retrieval Intervals are defined in the configuration for the Modbus outstation). The SCADAPack Modbus driver is an advanced driver and uses different settings to determine what registers are polled and when they are polled.Įach SCADAPack Modbus point has a unique address that corresponds to a register in the Modbus outstation. As the Input Discrete range is 100001 to 165536, this means the Modbus driver will poll the address range 100011 to 100026.įor more information on Modbus configuration, see the ClearSCADA Help. So, if the Location is Input Discretes, the Data Address is 10 and the Data Length is 15, the Modbus driver will poll 15 registers, starting from the 10th register in the Input Discrete range. The Modbus driver always polls the entire range of registers (the range defined by the Data Address and Data Length settings in the Modbus Scanner configuration).
You can specify the range when you configure a Modbus scanner in the ClearSCADA database (in the Data Address and Data Length fields). The Modbus driver scans a defined range of registers.
Both polling methodologies are described below. SCADAPack Modbus is an advanced driver and uses a different polling methodology. The Modbus driver uses a specific polling methodology (the Modbus Slave driver does not poll data). Modbus (and Modbus Slave) are both simple drivers. While both protocols can read from generic Modbus devices, there are differences in the polling methodology used in each. Elektrik Tasarım Dağıtım ve Uygulama ÇözümleriĬlearSCADA contains both a Modbus and SCADAPack Modbus protocol driver.Motorabgangstechnik & Antriebstechnik Forum.Level and Pressure Instrumentation Forum.EcoStruxure Automation Expert / IEC 61499 Forum.APC UPS Data Center Backup Solutions Forum.APC UPS, Critical Power, Cooling and Racks.