Multiple Register Writes; Request Packet Sizes - Newport PLATINUM Series Manual

DasyLab Platinum Modbus Interface
The access can be split into 2 consecutive single register reads. When the lower (base) register is
accessed the entire 32 bit entity is read and the two most significant bytes are returned. The following
single register read must specify the next consecutive register address. The two least significant
bytes of the internally buffered data used in the response.
Attempts to access the two least significant bytes without first reading the two most significant bytes
will result in an error response.

2.2.2 Multiple Register Writes

When writing a dual register entity the lower order register should be used as the requested 'holdiing
register', with a request for minimum of 2 registers. The write data is internally buffered and
transferred to the database entry as a 32 bit value.
The access can be split into 2 consecutive single register writes. When the lower (base) register is
written the 16 bit entity is internally buffered BUT NO DATA TRANSFER IS MADE TO THE
DATABASE. The following single register write must specify the next consecutive register address.
The two least significant bytes of the write request are combined with the previous write data and the
entire 32 bit entity is written to the database.
Attempts to write the two least significant bytes without first writing the two most significant bytes will
result in an error response.
Data Number
Types of
Registers
Boolean 1
Byte, 1
Char
Int16, 1
uint16
Int32, 2
uint32
float 2

2.2.3 Request Packet Sizes

Multiple consecutive registers may be accessed in a single transaction.
The Platinum Modbus interface imposes a maximum of 64 bytes for the total transaction. Allowing for
the required framing, addressing and integrity checks results in the following data size restrictions
using the READ and WRITE MULTIPLE functions.
Format Protocol Overhead
ASCII 16
RTU 8
TCP/IP 8
Document Number
For Internal Use Only: This document contains confidential, proprietary information of Omega Engineering/Newport Electronics,
The Document may not be copied or reproduced without the prior, written permission of Omega Engineering/Newport Electronics
Byte
0 1 2
-- LSB
-- LSB
MSB LSB
0 1 2
MSB B-1 B-2
Sign+ Mantisa B-1
Exp MSB
Maximum Read data
12 Registers
23 Registers
23 Registers
Revision 1.0
Description
3
Zero = OFF, non-zero = ON
Entity contained in LSB of register,
N/A
Byte 0 ignored.
Entity contained in MSB/LSB of
register.
3 (dual register data)
LSB Requires 2 consecutive registers,
MSB transferred first
Mantisa IEEE formatted value contained in 2
LSB consecutive register
Maximum Write data
12 Registers
23 Registers
23 Registers
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