C51: Reentrancy Issues With the Dallas 390 Math Accelerator

Information in this article applies to:

• All C51 Versions

QUESTION

Is the Maxim (formerly Dallas Semiconductor) 390 math accelerator reentrant, e.g., can the math accelerator be used in the main C program and in an interrupt?

ANSWER

No. Math operations performed using the math accelerator are not reentrant. The following suggestions will help to guarantee that only one thread of execution uses the arithmetic processor.

• Use the MODDA directive to compile either
  • Functions which are guaranteed to execute only in the main program,
  • or Functions used by one interrupt service routine.
• Compile all remaining functions with the NOMODDA directive.

MORE INFORMATION

• Refer to MODDA in the Cx51 User's Guide.
• Refer to NOMODDA in the Cx51 User's Guide.
• C51: Maxim 390 Math Accelerator Operations
• C51: Maxim 390 Hangs on Math Operations

SEE ALSO

• C51: Memory Types for Maxim 390 Contiguous Mode
• C51: Configuring Dallas 390 and 400 for Contiguous Mode
• MON390: CANNOT CONNECT TO DALLAS DS80C400 ON THE DS-TINI-1 B
• µVision DEBUGGER: Debugging With Maxim/Dallas DS5250 Monitor

Last Reviewed: Thursday, February 25, 2021