DSP2812例程BLDC3_1中DATALOG模块的疑问

#ifndef __DLOG4CH_H__
#define __DLOG4CH_H__
 
#define NULL    0
 
typedef struct {    long  task;          // Variable:  Task address pointer  
                    int  *iptr1;         // Input: First input pointer (Q15)     
                    int  *iptr2;         // Input: Second input pointer (Q15)        
                    int  *iptr3;         // Input: Third input pointer (Q15) 
                    int  *iptr4;         // Input: Fourth input pointer (Q15) 
                    int  trig_value;     // Input: Trigger point (Q15)       
                    int  prescalar;      // Parameter: Data log prescale     
                    int  skip_cntr;      // Variable:  Data log skip counter     
                    int  cntr;           // Variable:  Data log counter      
                    long write_ptr;      // Variable:  Graph address pointer              
                    int  size;           // Parameter: Maximum data buffer    
                    int  (*init)();      // Pointer to init function         
                    int  (*update)();    // Pointer to update function        
               } DLOG_4CH;               
                                                        
typedef DLOG_4CH *DLOG_4CH_handle;                           
                                                        
void DLOG_4CH_init(void *);
void DLOG_4CH_update(void *);                                                        
                                                        
/*=============================================================================
Default initalizer for the DLOG_4CH object.
==============================================================================*/
                    
#define DLOG_4CH_DEFAULTS { 0UL, \
                            NULL, \
                            NULL, \
                            NULL, \
                            NULL, \
                            0, \
                            1, \
                            0, \
                            0, \
                            0UL, \
                            0x400, \
                            (int (*)(int))DLOG_4CH_init, \
                            (int (*)(int))DLOG_4CH_update }

#endif

         其初始化语句如下：

// Initialize DATALOG module       
    dlog.iptr1 = &DlogCh1; 
    dlog.iptr2 = &DlogCh2;
    dlog.iptr3 = &DlogCh3;
    dlog.iptr4 = &DlogCh4;
    dlog.trig_value = 0x01;
    dlog.size = 0x400;
    dlog.prescalar = 1;
    dlog.init(&dlog);