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User Manual Chapter 13

GFK-1742F Jan 2020

Local Logic Variables 310

13.2.3 System_Halt Variable

The System_Halt variable is a Write-Only Bit Operand (refer to Table 69). If the Local Logic

program writes a 1 to the System_Halt variable servo motion and Local Logic execution is

halted. An error code is also reported in the Module Status Code ( refer to Chapter 12). Thus

the System_Halt variable can be used to trap for fatal error conditions and perform error

recovery. The sample code below shows a possible scenario in which the System_Halt

variable might be used:

IF Overflow THEN (* Trap for an overflow *)

System_Halt := TRUE; (* Halt Local Logic Execution and Servo Motion *)

END_IF;

13.3 Double Precision 64 Bit Registers

Local Logic provides eight 64-bit registers (D00-D07) in addition to the 255 32-bit registers

(refer to Table 69). This is to allow the user to store the result of multiplying two 32-bit

numbers in a Dxx register and then perform a Divide/Modulus operation on the result.

Thus the 64 bit registers may be used under the following circumstances:

As the Destination register for a multiply operation.

As the Dividend (numerator) in a Divide/Modulus operation.

The Parser will flag an error if it is used in other operations. Example code for the use of the

Dxx registers is shown below:

D01:= P001 * 2147483647; (* Perform a Multiply operation and store in a 64 bit register

P010:= D01 / 12500; (* Divide the result and store in a 32 bit register *)

Note that the above scenario may result in a Divide Overflow, if the result does not fit in a

32-bit register. A Divide Overflow will halt Local Logic execution and servo motion, since the

result of the operation is undefined (refer to Chapter 12). An error code will also be reported

in the Module Status Code.

Note: The contents of the 64-bit data registers (D00-D07) and 32-bit writeable data registers (P000-

P255) are not automatically initialized by Local Logic when it starts running. The user should

initialize any required variables using a separate Local Logic program or the

First_Local_Logic_Sweep variable or host controller ladder program.

Emerson DSM314 User Manual

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