Hach sc200, User Manual

Page: 277 / 875

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 END SIZE IN ACCESS
ADDRESS ADDRESS WORDS
ModBUS Data Table
Start Base Address
1000 1000 1 Read/Write
Factory Configuration
Data
Base+1 Base+18 18 Read Only
User Configuration
Data
Base+101 Base+148 48 Read/Write
Status Information Base+201 Base+253 53 Read Only
Control Words
Base+301 Base+302 2 Read/Write
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 ADDRESS POSSIBLE VALUES
ModBUS Data
Table Base Address
1000 1000 - 60,000
(default 40,000)
• 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.
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