Motorola MPC860 PowerQUICC User Manual page 694

Part V. The Communications Processor Module
last buffer of a frame contains the total number of frame bytes, including the 2 or 4 bytes
for CRC. Figure 24-6 shows an example of how RxBDs are used in receiving.
E
Status 0
Length
Pointer
E
Status 0
Length
Pointer
E
Status 0
Length
Pointer
E
Status 1
Length
Pointer
F A A C
Two Frames
Received in HDLC
Time
Legend:
F = Flag
A = Address Byte
C = Control Byte
I = Information Byte
CR = CRC Byte
Figure 24-6. SCC HDLC Receiving using RxBDs
24-10
Receive BD 0
L F
0 1
0x0008
32-Bit Buffer Pointer
Receive BD 1
L F
1 0
0x000B
32-Bit Buffer Pointer
Receive BD 2
L F AB
1 1 1
0x0003
32-Bit Buffer Pointer
Receive BD 3
XXXX
32-Bit Buffer Pointer
Stored in Rx Buffer
I I I I I I CR CR F
MPC860 PowerQUICC UserÕs Manual
MRBLR = 8 Bytes for this SCC
Address 1
Address 2
Buffer Full
Control Byte
Information
(I-Field) Bytes
Last I-Field Byte
CRC Byte 1
Buffer Closed
CRC Byte 2
when Closing Flag
Received
Empty
Address 1
Address 2
Abort was
Control Byte
Received after
Control Byte
Empty
Empty
Buffer
Still Empty
Stored in Rx Buffer
Line Idle F A
Buffer
8 Bytes
5
Buffer
8 Bytes
Buffer
8 Bytes
Buffer
8 Bytes
A C Abort/Idle
Unexpected Abort Present
Occurs before Time
Closing Flag
MOTOROLA