C51: Function Pointers in Contiguous Mode

Information in this article applies to:

• C51 All Versions
• C51 Version 7.10

QUESTION

I am using the following code with a Maxim (formerly Dallas Semiconductor) 390 target in Contiguous Mode (program size up to 16MB). However, function pointers that are defined with the code attribute fail.

The following program does not work:

typedef void (code *FUNCT_PTR_V_V)(void);
unsigned char IntSrc0;
static void function_0(void){ IntSrc0=0x00; }
static void function_1(void){ IntSrc0=0x01; }

const  FUNCT_PTR_V_V code function_table2[2] ={ function_0, function_1 };

void main(void){
  function_table2[0]();   // function pointer is loaded with invalid value
  while(1);
}

Why do I have this problem?

ANSWER

When working in the Contiguous Mode, you must use generic pointers as function pointers. Only generic pointers store the complete address information which is required. So you need to define the function pointer as shown below:

typedef void (*FUNCT_PTR_V_V)(void);

MORE INFORMATION

• C51: Configuring Dallas 390 and 400 for Contiguous Mode
• C51: Absolute Memory Accesses to Maxim 390 Far Memory
• Dallas Semiconductor DS80C390 in the device database.
• More information about the Dallas 390 support may be found in the README.TXT file found in the \KEIL\C51\EXAMPLES\DALLAS 390 directory of your installation.

SEE ALSO

• C51: Maxim 390 Math Accelerator Operations
• C51: Memory Types for Maxim 390 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