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0 =The data buffer associated with this BD has been filled with received
data, or data reception has been aborted due to an error condition.
The M6800 core is free to examine or write to any fields of the BD.
X - External Buffer
1 =The buffer associated with this BD is in external memory.
O=The buffer associated with this BD is in internal dual-port RAM.
W - Wrap (Final BD in Table)
1 =This is the last BD in the Rx BD table. After this buffer has been used,
the DDCMP controller places incoming data in to the first BD in the
table.
0 =This is not the last BD in the Rx BD table.
NOTE
The user is required to set the wrap bit in one of the first eight BDs;
otherwise, errant behavior may occur.
I - Interrupt
1 =The M68000 core is interrupted when this buffer has been closed by
the DDCMP controller.
0= No interrupt is generated after this buffer has been closed.
The following status bits are written by the DDCMP controller after it has
finished receiving data in the associated data buffer.
L - Last in Message
1 =The buffer is the last in a message.
0 =The buffer is not the last in a message.
H - Header in Buffer
1 =The buffer contains a message header.
0 =The buffer does not contain a message header.
NOTE
To correctly identify buffers containing headers, the buffer size should
be eight or more bytes in length.
T2,T1 - Message Type
00 = Data message
MOTOROLA
01 =Control message
10= Maintenance message
11 =Reserved
MC68302 USER'S MANUAL
4-97
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