Rockwell Automation SD3000 Drive Configuration, Programming - Manual (Page 60)

The following data types can be defined in the application register area: boolean (bit), integer (16
bits), double integer (32 bits), and real (32 bits). Because of the way in which read and write
operations occur in the UDC dual port memory, however, the programmer must assign boolean
variables carefully within pairs of 16-bit registers.
The UDC operating system generally operates on the amount of memory called for by the data type,
e.g., when it is requested to write to a 16-bit (integer) value, it writes only to those specific 16 bits.
However, in the case of boolean variables, the UDC operating system always operates on 32 bits at a
time. It is not possible for the operating system to write to only one bit within a register. The remaining
31 bits in the register pair will be written over as well, possibly resulting in corrupted data.
Within any pair of 16-bit registers beginning on an even number boundary, i.e., registers 300 and
301,302 and 303 (but not registers 301 and 302), all boolean variables must be either inputs or
outputs. If there are no bits assigned within a particular register pair, then one 16-bit register can be
an output and the other 16-bit register can be an input, or both can be inputs or outputs.
Alternatively, the entire register pair can be defined as a real or double integer value.
Note that if you are referencing a 32-bit value (real or double integer) in the UDC dual port from an
AutoMax task, the operation is being performed by the AutoMax Processor, which operates on 16 bits
of data at a time. In such a situation, you must employ some form of software handshaking in the
AutoMax task to ensure that both the upper and lower order 16 bits represent the current value of the
variable. This is required for 32-bit values in the “every” scan register range. It is possible to use
software “flags” to indicate that data can be read. It is also possible to read the data multiple times
(typically three times) and compare the values.
3.6 UDC Module Test I/O Registers (Registers
10004017)
This view is used to configure the UDC module’s Test Switch Inputs Register and the Meter Port
Setup Registers.
3.6.1 UDC Module Test Switch Inputs Register (Register 1000)
This view is used to configure the register that displays the status of the test switches and LED
indicators on the UDC module. Writing to this register will not change the state of the LEDs. The
status of this register is retained during a Stop All.
Bit: 0
Hex Value:
0001 H
Sug. Var. Name: UDC_PB@
Range: N/A
Access: Read only
UDC Error Code: N/A
LED: N/A
Description: The Pushbutton Input bit is on when the pushbutton is pressed.
Bit: 1
Hex Value: 0002H
Sug. Var. Name:
SWIT_UP@
Range: N/A
Access: Read only
UDC Error Code: N/A
LED: N/A
Description: The Switch Up Input bit is on when the switch is in the up position.
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