1. First you need to know the point index of the first Modbus Holding Register where
the string can be accessed; refer to J.5 for mapping details.
2. Issue a Read Holding Registers command with this point index as start register.
Since you can’t read the complete 128 registers in a single Modbus query, the
embedded device always buffers the last string object accessed.
3. Issue another Read command for the rest of the string, and the string integrity is
preserved.
J.4.2 Data access - write to H201Ti via Modbus
Hydran 201Ti supports following actions that can be performed via Modbus:
• Acknowledge pending alarms;
• Set Hydran 201Ti system date and time.
These actions can be performed by issuing Modbus commands with function codes
05 (Force single coil), 15 (Force multiple coils), 06 (Preset single holding register) or 16
(Preset multiple holding registers) to corresponding registers or coils.
To prevent accidental modification of Hydran 201Ti settings or behavior, all Modbus
registers that allow modification are write-protected. To unlock the write protection
mechanism, Level 1 password has to be written to the SCADA Password holding register.
See chapter 5.4 Passwords for the password value. After it is done, write protection
mechanism stays unlocked until a time-out of 10 minutes expires or an invalid password
value is written to the SCADA Password register.
J.4.2.1 Acknowledging Pending Alarms
If a particular alarm needs acknowledge, corresponding binary value (Modbus coil)
Alarm_XXXXX_Pending will be in active state. The alarm can be acknowledged by issuing
Modbus command 05 (Force single coil) to the corresponding binary register. Multiple
alarms can be acknowledged by issuing command 15 (Force multiple coils) with a range
of Alarm Pending status binary registers.
The steps to acknowledge pending alarms are as follows:
1. Write Level 1 Password to the SCADA Password holding register.
2. Issue one or more Binary Write commands to acknowledge pending alarms.
3. Write 0 to the SCADA Password holding register.
The last step is optional; it ensures that write protection mechanism engages as soon as
write access is completed, without waiting for the timeout to expire.
See chapter 5.4 Passwords for the password value.
See chapter J-5 below for addresses of the Modbus registers.
J.4.2.2 Setting Hydran 201Ti System Date and Time
The Hydran 201Ti supports changing its system date and time via Modbus. This can
be accomplished by writing a 32-bit integer Unix time value to the System Date holding
register.
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