GE Industrial Solutions POWER LEADER ModBus Monitor - Manual (Page 52)

POWER LEADER Modbus Monitor
Chapter 7 – Advanced Configuration
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register. The user can only define a data format from the
list of available formats for the device.
Generic Device Types
Generic device types do not support:
•
event logging
•
special handling registers
•
register data formats other than those shown in
Appendix C
Registers can only be displayed by the Modbus Monitor
if their data formats are recognized by the Monitor. If a
register has any special processing or is an unsupported
data format, the Monitor will not correctly interpret and
display the information.
Generic device types must also be able to support system
communications at 150 milliseconds or faster to be
compatible with the Modbus Monitor. This ‘protocol
timer tick’ is the rate at which the Monitor will query
devices. Every ‘tick’ (150 ms) the Monitor will perform
a network communications action (speaking on the
network). If a generic device cannot keep up with the
potential of one message every 150 milliseconds, the
device will cause communications errors.
Defining Hybrid and Generic Device Types
The Modbus Monitor allows a maximum of 300 registers
to be defined and displayed. The screen formats chosen
for the pages of a device dictate the actual number of
registers that can be displayed for a device. Screen
Format #1 allows 30 registers to be displayed, so having
10 Format #1 pages will allow 300 displayable registers.
Screen Format #3 allows 14 registers to be displayed, so
having 10 of these pages will give 140 displayable
registers. The actual number of registers displayable at
the Modbus Monitor is dictated by the types of screens
defined using Modbus Monitor Configuration Tool and
ranges from a minimum of 140 registers to a maximum
of 300 registers.
It is recommended that when you create a generic or
hybrid device, you define all the device type’s registers
first, then customize the display screens. This way you
will have the full list of registers to select from when you
create the display screens.
Defining the Register Set
The Modbus Monitor represents devices by defining a
set of registers for that device. For each register, the
Modbus Monitor requires a register mnemonic, register
type, register address (index), register format and scaling
factor.
The register mnemonic is used by the Modbus Monitor
Configuration Tool to give the register a useful meaning.
The register address is the decimal address of the
register. The register type specifies to the Modbus
Monitor whether the register is a Coil, Contact, Input, or
Holding register. The register format specifies how to
display the register at the Modbus Monitor, and the
scaling factor is a multiplier that specifies a value to
multiply the register data by before displaying it on the
screen.
The Modbus Monitor supports any register within the
extended Modbus address range (0 - 65535), as does
PMCS 6.0. When a register is defined at the user
interface, the Modbus Monitor will request that register
from the device when needed. If the register is not valid
the Modbus Monitor will still request the register.
As discussed earlier in the section titled Utilized
Register Block List (URBL), the Modbus Monitor
allows the user to specify up to 10 blocks of registers for
each type of register. A block of register is defined as a
contiguous sub-set of registers within the current set of
defined registers. If a gap occurs within the register set a
new block is generated. This is to prevent the Modbus
Monitor from requesting an invalid register address
range from a device (thus not updating any register
within that request). Each block can contain a maximum
of 125 registers as per the Modbus specification. The
worst case would allow the user to define only 10
registers.
For example, if the user defines the following registers
in the Modbus Monitor Configuration Tool R40000,
R40010, R40020, R40030, R40040, R40050, R40060,
R40070, R40080 and R40090. The configuration tool
would generate 10 separate register blocks for the R4
type registers. The Configuration Tool has no way to be
sure whether the registers between the defined registers
are valid. If all the registers from R40000-R40090 are
defined at the Configuration Tool, it would only generate
one register block list consisting of a request for all the
registers.