Figure 4-27. Hdlc Receive Bd Example - Motorola MC68302 User Manual

Communications Processor (CP)
E
0
STATUS
LENGTH
32-BIT BUFFER POINTER
POINTER
E
STATUS 0
LENGTH
32-BIT BUFFER POINTER
POINTER
E
0
STATUS
LENGTH
32-BIT BUFFER POINTER
POINTER
E
1
STATUS
LENGTH
32-BIT BUFFER POINTER
POINTER
STORED IN RX BUFFER
F A A C
TWO FRAMES
RECEIVED IN HDLC
TIME
LEGEND:
F = FLAG
A = ADDRESS BYTE
CR = CRC BYTE
C = CONTROL BYTE
4-76
RECEIVE BD 0
L F
0 1
0008
(24-BITS USED)
RECEIVE BD 1
L F
1 0
000B
(24-BITS USED)
RECEIVE BD 2
ID AB
1
1 1
0003
(24-BITS USED)
RECEIVE BD 3
XXXX
(24-BITS USED)
I I I I I I CR CR F
I = INFORMATION BYTE

Figure 4-27. HDLC Receive BD Example

MC68302 USER'S MANUAL
MRBLR = 8 BYTES FOR THIS SCC
BUFFER
ADDRESS 1
ADDRESS 2
CONTROL BYTE
BUFFER
FULL
INFORMATION
(I-FIELD) BYTES
BUFFER
LAST I-FIELD BYTE
CRC BYTE 1
CRC BYTE 2
BUFFER
CLOSED WHEN
EMPTY
CLOSING FLAG
RECEIVED
BUFFER
ADDRESS 1
ADDRESS 2
CONTROL BYTE
ABORT WAS
RECEIVED
EMPTY
AFTER CONTROL
BYTE!
BUFFER
EMPTY
BUFFER
STILL
EMPTY
STORED IN RX BUFFER
LINE IDLE F A A
UNEXPECTED ABORT
OCCURS BEFORE
CLOSING FLAG!
8 BYTES
5
8 BYTES
8 BYTES
8 BYTES
C ABORT/IDLE
PRESENT
TIME
MOTOROLA