Figure S-1 The fields in the SDLC frame are as follows: • Flag: A specific eight-bit pattern that alerts the receiving device to the transmission of the frame.The most commonly used flag character is 01111110, in binary notation (7E in hexadecimal). Flags also fill idle time on the line with a flag between each frame. A flag is also included at the end to alert the receiving device to the end of the transmission. • Address: An eight-bit field that identifies the address of the target station, a group address for multiple target stations, or a broadcast address to all stations.This field also can be used to distinguish commands from responses. 74570c19.qxd 9/12/07 12:41 AM Page 429 |