5.2. L2_BLK

The L2_BLK data structure is used to send or receive a frame of information to or from the data link layer using the gc_SndFrame( ) or the gc_GetFrame( ) function. See example code for these functions in the Global Call API Library Reference for details.

The L2_BLK data structure is defined as follows:

#define MAXLEN_IEDATA    254
typedef struct
  {
   char sapi;
   char ces;
   short length;
   char data[MAXLEN_DATA];
   } L2_BLK, *L2_BLK_PTR;  

See Table 37 for descriptions of the L2_BLK fields.

Table 37. L2_BLK Fields 

Field	Description
sapi	service access point ID (always set to 0)
ces	connection endpoint suffix When using Springware boards: set to 0 When using DM3 boards: set to 1
length	Length of data block in bytes. Value must be less than MAXLEN_IEDATA as defined in gcisdn.h.
data[MAXLEN_IEDATA]	Data for frame. Must be formatted to meet CCITT recommendations. The maximum length of the data field is MAXLEN_IEDATA.

The following L2 block structure can be passed to the function via the GC_L2_BLK structure. */

     l2_blk_ptr[0] = 0x08;     /* Protocol discriminator */
     l2_blk_ptr[1] = 0x02;     /* CRN length - 2 bytes */
     l2_blk_ptr[2] = 0x03;     /* CRN = 8003 */
     l2_blk_ptr[3] = 0x80;
     l2_blk_ptr[4] = 0x6e;     /* msg type = NOTIFY */ 
     /* The first IE */
     l2_blk_ptr[5] = 0x27;     /* IE type = 27 (NOTIFY) */
     l2_blk_ptr[6] = 0x01;     /* The length of NOTIFY */
     l2_blk_ptr[7] = 0xF1;     /* Notify indication */ 
     /* The second IE */
     l2_blk_ptr[8] = 0x76;     /* IE type = 76 (REDIRECTION) */
     l2_blk_ptr[9] = 0x03;     /* length of redirection */
     l2_blk_ptr[10] = 0x01;    /* unknown type and E164 plan */
     l2_blk_ptr[11] = 0x03;    /* network provides presentation */
     l2_blk_ptr[12] = 0x8D;    /* reason = transfer */ 

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