Technical Instructions
Modbus RTU Interface Module for SED2
Document Number 155-767
February 25, 2009
Page 10
Siemens Industry, Inc.
Interface Module
Registers
The following tables contain the lists of all Interface Module holding Registers available
on the Interface Module. The Interface Module host may write to Registers 40001
through 40023. All other Registers are read only.
There is a scaling factor included for some of the Registers. Because Modbus does not
represent floating point numbers, all floating point values in the drive are converted to
integer register values by applying a scaling (multiplication) factor. The scaling factors
are in the range of 10 to 1000.
For example:
ACCEL TIME has a scaling factor of 100. If the SED2 contains a
value of 20.50, then the ACCEL TIME register will contain a value of 2050.
FREQ REF (40003) and FREQ ACTUAL
(40063) are special case Registers. FREQ
REF contains the raw integer value passed in the HSW portion of a USS protocol
request to the SED2 drive. FREQ Actual contains the raw integer value passed in the
HIW portion of a USS protocol response from the SED2. Both Registers are scaled so
that a value of 4000th represents 100% of the actual frequency.
FREQ SCALED (40044)
contains a scaled version of the HIW data, so that a value of
2000 in the register represents the value 4000h in the USS protocol response (and
100% of the maximum frequency).
STW
and
HSW
refer to the 1st and 2nd control words, respectively, of PZD data
included in every poll sent from the Interface Module to the SED2 drive via the USS
protocol. ZSW and HIW refer to the 1st and 2nd status words, respectively, of PZD data
included in every poll response from the SED2 drive to the Interface Module via the USS
protocol. Registers mapped to PZD data are updated frequently.
All other parameters (except WDOG ACTION and WDOG TIME), which are handled
internally in the Interface Module, are mapped to parameters in the SED2 drive, and are
updated cyclically.
•
Registers mapped to monitor parameters
—
such as CURRENT or SPEED, whose values change automatically during
normal operation of the drive, without the intervention of an operator—are
updated at a rate of approximately once per second.
•
Registers mapped to setup parameters
—such as ACCEL TIME or FREQ
MAX, whose values typically change only via intervention by an operator—are
updated at a rate of approximately once every five seconds.
