ABB Remote I/O RIO600, Руководство по установке и пусконаладке

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7.1.11 Data mapping principles
Modbus data is organized sequentially. This is the most efficient organization method
since the master normally scans the Modbus data in blocks.
7.1.12 Default data organization
The available Modbus data in RIO600 is always mapped to a Modbus location. The
Modbus points that are pre-mapped are only cached from the application by the stack
when there is a read poll for the corresponding data point.
7.1.13 Data in monitoring direction
All data in the monitoring direction is available through the 3X and 4X memory areas.
This includes the digital indication data which is also readable in the 1X and 0X areas.
All register structures are located in the 4X area. The Modbus data may contain empty
bits or registers within the sequential data areas. These bits and registers are intended
for possible future expansion. Reading this data does not result in any Modbus
exception response. The value in these bits or registers is always zero.
7.1.14 One-bit data mapping
All one-bit data is readable either from the 0X or 1X memory area. The Modbus bit
point addresses are similar regardless of the memory area. The same one-bit data can
also be read either from the 3X or the 4X area. In this case, the bit values are packed
into 16 bit 3X and 4X registers. Controls and set points are mapped to Modbus 0X data
(coils). Only one coil can be operated at a time. Some control bits are packed bits in
the 4X control register structures.
7.1.15 Digital input data
As the indication signals related to fault detection applications often change rapidly,
the Modbus master may not detect all the changes. The Modbus protocol
implementation in RIO600 supports the latching concept for binary input data points.
The
Binary Input Read Method , found under Parameter Setting in PCM600, can be
configured either as "Instantaneous" or "Latched".
In instantaneous mode, the Modbus master receives the latest values of binary data
points for every read poll. In latched mode, the Modbus master receives the first
changed value of the corresponding data point since the last read poll has been made
for the same data point. The actual present value is reported in the next read poll.
In this way, a missed event between data polls can be detected. The latching concept
is applicable only for all the binary channels of DIM module, all the binary readable
points of SIM8F/SIM4F module and all the binary channels of SCM module for the
4I4O application type.
Section 7
1MRS757488 H
Modbus TCP communication
174 RIO600
Installation and Commissioning Manual