Common External Message Interface (EMI) defines two control fields in its frame format (one byte each).
Control Field 1
Bit |
------+---------------------------------------------------------------
7 | Frame Type - 0x0 for extended frame
| 0x1 for standard frame
------+---------------------------------------------------------------
6 | Reserved
|
------+---------------------------------------------------------------
5 | Repeat Flag - 0x0 repeat frame on medium in case of an error
| 0x1 do not repeat
------+---------------------------------------------------------------
4 | System Broadcast - 0x0 system broadcast
| 0x1 broadcast
------+---------------------------------------------------------------
3 | Priority - 0x0 system
| 0x1 normal
------+ 0x2 urgent
2 | 0x3 low
|
------+---------------------------------------------------------------
1 | Acknowledge Request - 0x0 no ACK requested
| (L_Data.req) 0x1 ACK requested
------+---------------------------------------------------------------
0 | Confirm - 0x0 no error
| (L_Data.con) - 0x1 error
------+---------------------------------------------------------------
Control Field 2
Bit |
------+---------------------------------------------------------------
7 | Destination Address Type - 0x0 individual address
| - 0x1 group address
------+---------------------------------------------------------------
6-4 | Hop Count (0-7)
------+---------------------------------------------------------------
3-0 | Extended Frame Format - 0x0 standard frame
------+---------------------------------------------------------------