Motorola MPC8260 - Manual (Page 600)

20-16 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA
Part IV. Communications Processor Module
¥ An ENTER HUNT MODE or CLOSE RXBD command is issued.
¥ An address character is received in multidrop mode. The address character is written
to the next buffer for a software comparison.
Figure 20-7 shows an example of how RxBDs are used in receiving.
Figure 20-7. SCC UART Receiving using RxBDs
Byte 5
Buffer
0
0008
32-Bit Buffer Pointer
0
E ID
Rx BD 0
Status
Length
Pointer
0
0002
32-Bit Buffer Pointer
1
E ID
Rx BD 1
Status
Length
Pointer
0
0004
32-Bit Buffer Pointer
0
E ID
Rx BD 2
Status
Length
Pointer
1
XXXX
32-Bit Buffer Pointer
E
Rx BD 3
Status
Length
Pointer
Byte 1
Byte 2
Byte 8
Buffer
Byte 9
Byte 10
Buffer
Byte 1
Byte 2
Byte 3
Buffer
Byte 4 Error!
Empty
Additional Bytes
will be Stored Unless
Idle Count Expires
(MAX_IDL)
8 Bytes
8 Bytes
8 Bytes
8 Bytes
Characters
Received by UART
Fourth Character
10 Characters
Long Idle Period
has Framing Error!
Present
Time
Time
5 Characters
Buffer Full
Idle Time-Out
Occurred
Byte 4 has
Framing Error
Reception
Still in Progress
with this Buffer
1
FR
etc.
Empty
MRBLR = 8 Bytes for this SCC