Modbus Base Address (Read/Write); Table 3-2. Modbus Memory Map Overview - MSA Ultima Instruction Manual Addendum

Table 3-2. ModBUS Memory Map Overview

The Modbus port allows for access to a significant amount of information which may be
necessary for your system integration requirements. As a minimum, the gas readings and
fault status registers should be polled.
DESCRIPTION START
ADDRESS
ModBUS Data Table
Start Base Address 1000
Factory Configuration
Data Base+1
User Configuration
Data Base+101
Status Information Base+201
Base+301
Control Words

ModBUS Base Address (Read/Write)

The ModBUS base address register is located at address 1000 and has
a default value of 40,000.
• This may be changed by writing a new value within the permissible
range to that address.
• Subsequent addresses must take this new base address into
consideration.
• The base address may be changed by writing to address 1000,
regardless of its contents.
Table 3-3. ModBUS Bas Address (Read/Write)
DESCRIPTION
ModBUS Data
Table Base Address
• For systems that use five-digit addressing, 4XXXX:
• If the first digit is an internal system requirement and does not
appear in the communications packet, write the value 1000 to
address 41000. The base address is now 41000 and the first
valid address is 41001.
• If all five digits appear in the communications packet, the
default base address is 40000 and the first valid address is
40001.
3-2
END SIZE IN
ADDRESS WORDS
1000 1
Base+18 18
Base+148 48
Base+253 53
Base+302 2
ADDRESS POSSIBLE VALUES
1000 1000 - 60,000
(default 40,000)
ACCESS
Read/Write
Read Only
Read/Write
Read Only
Read/Write