9.2.4 Internal Local Registers (Slave ID 199) for the DXM100 and
DXM150
The main storage elements for the DXM are its Local Registers, which can store 4-byte values that result from register
mapping, action rules, or ScriptBasic commands.
•
Local Registers 1 through 850 are standard 32-bit unsigned registers.
•
Local Registers 851 through 900 are non-volatile registers that are limited to 100,000 write cycles.
•
Local Registers 1001 through 1900 are floating point format numbers. Each register address stores half of a floating
point number. For example, registers 1001 and 1002 store the first full 32-bit floating point number.
•
Local Registers 10001 through 19000 are system, read-only, registers that track DXM data and statistics.
Table 39: Modbus Registers for Internal Local Registers (Modbus Slave 199)
Local Registers
Type
Description
1–845
32-bit unsigned
Internal processor memory
846–849
32-bit unsigned
Reset, Constant, Timer
851–900
32-bit unsigned
Data flash, non-volatile
1001–1900
32-bit IEEE Floating Point
Floating point registers, internal processor memory
> 10000
Read-only virtual registers
Local Registers 1–850 (Internal Processor Memory, 32-bit, Unsigned)
—The Local Registers are the main global pool of
registers. Local Registers are used as basic storage registers and as the common data exchange mechanism. External
Modbus device registers can be read into the Local Registers or written from the Local Registers. The DXM, as a Modbus
master device or a Modbus slave device, exchanges data using the Local Registers. Modbus over Ethernet (Modbus/TCP)
uses the Local Registers as the accessible register data.
Local Registers 851–900 (Data Flash, Non-volatile, 32-bit, Unsigned)
— The top 50 Local Registers are special non-
volatile registers. The registers can store constants or calibration type data that must be maintained when power is turned off.
This register data is stored in a data flash component that has a limited write capability of 100,000 cycles, so these registers
should not be used as common memory registers that change frequently.
Local Registers 1001–1900 (32-bit IEEE Floating Point)
— These Local Registers are paired together to store a 32-bit
IEEE floating point format number in big endian format. Registers 1001 [31:16], 1002 [15:0] store the first floating point value;
registers 1003, 1004 store the second floating point number. There are a total of 500 floating point values; they are
addressed as two 16-bit pieces to accommodate the Modbus protocol. Use these registers when reading/writing external
devices that require Modbus registers in floating point format. Since Modbus transactions are 16-bits, the protocol requires
two registers to form a 32-bit floating point number.
Virtual Registers
— The DXM has a small pool of virtual registers that show internal variables of the main processor. Some
register values will be dependent upon the configuration settings of the DXM. Do not use
Read Rules
to move Virtual Local
Registers data into Local Registers. Use the
Action Rule
>
Register Copy
function to move Virtual Local Registers into
Local Registers space (1-850).
Table 40: Virtual registers
Virtual Registers
Definition
10001
GPS latitude direction (N, S, E, W)
GPS Coordinate Data if the DXM is configured to read an external GPS unit.
10002
GPS latitude
10003
GPS longitude direction (N, S, E, W)
10004
GPS longitude
10011–10012
Resync timer
Engineering use
10013–10014
Resync timer rollover
Engineering use
10015–10016
Reboot cause (Restart Codes above)
Reboot Type
10017–10018
Watchdog reset count
Counter to track how many resets have been caused by the Watchdog
10021
IO Board Battery Voltage (mV)
mV
10022
IO Board - Incoming Supply Voltage (mV)
mV
10023
Cut-off Feature
0—No successful readings
1—Normal range
2—Cut-off engaged
Sure Cross
®
DXM150 and 1500-Bx Wireless Controllers
70
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