AERCO AM Series Boiler Modbus Interface Manual - Manual (Page 6)

AM Series Modbus Interface Manual
1.3 MODBUS HOLDING REGISTERS
Modbus communicates using words (the contents of 16bit holding registers). The data that is
offered is organized as a list of bytes.
Depending on the type of Modbus software used, the holding register addressing range starts
either at 0x0000 or at 0x0001. If your Modbus software starts addressing from 0x0000 you can
use the holding register addresses shown in the table above. If your Modbus software
addressing range starts at 0x0001 then add 1 to the holding register addresses listed in the
table above. This is also true for the various test tools available for Modbus.
1.3.1 Control Register
A special control register is implemented to secure certain modbus actions / commands. To
activate these actions / commands, first, the control register must be written.
CAUTION!
This must be done only when initiating a write command to a
holding register. Do not send this command when no write enable
is needed to prevent holding registers from being corrupted.
Control Register Parameter
Holding
Register
Access
Parameter Name
Automatic
Conversion
Range
R W
99 0063 X X Control register -
Bit0: Write enable
Bit14: Controller Reset
When no Modbus communication (reading or writing) is sensed for more than 4.0 Seconds
the control register bits will be reset. The bits will also be reset when undefined bits (i.e. other
than bits 0 and 14) are set.
1.3.1.1 Write Enable
The ‘Write enable’ register controls the reading and writing of the holding registers.
‘Write enable’ = 0:
the data in the holding register is read only.
‘Write enable’ = 1: the data in the holding register can be written.
CAUTION!
Writing of parameters with a different value is limited to 10,000
times. All (CH,DHW) set points and parameters are for preset only,
they can be changed with an average of two changes per day, but
are NOT to be used for dynamic temperature control!
1.3.1.2 Controller Reset
A controller may be reset (only) when it is in error. Only Lock out errors can be reset. When the
controller is in error, it can be reset by setting bit 14 to the control holding register (0x0063) of
the Modbus interface. The Interface board then sends a reset command to the controller over
the Argus Link bus. Once it has done this, it resets the reset bit of the Control holding register.
Page 6 of
18 AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, NY 10913
OMM-0102_0A
PRI: 09/22/2014
Phone: 800-526-0288
GF-146-MB