MC68000 MOTOROLA [Motorola, Inc], MC68000 Datasheet - Page 230

• Manufacturer Part Number: MC68000
• Manufacturer: MOTOROLA [Motorola, Inc]

Communications Processor (CP)
following message reception. Bit 15 determines whether the M68000 core or the CP may
currently access the BD.
E—Empty
X—External Buffer
W—Wrap (Final BD in Table)
I—Interrupt
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
H—Header in Buffer
4-110
0 = The data buffer associated with this BD has been filled with received data, or data
1 = The data buffer associated with this BD is empty. This bit signifies that the BD and
0 = The buffer associated with this BD is in internal dual-port RAM.
1 = The buffer associated with this BD is in external memory.
0 = This is not the last BD in the Rx BD table.
1 = This is the last BD in the Rx BD table. After this buffer has been used, the DDCMP
0 = No interrupt is generated after this buffer has been closed.
1 = The RBD or RBK bits in the DDCMP event register will be set when this buffer has
0 = The buffer is not the last in a message.
1 = The buffer is the last in a message.
0 = The buffer does not contain a message header.
1 = The buffer contains a message header.
reception has been aborted due to an error condition. The M6800 core is free to
examine or write to any fields of the BD.
its associated buffer are available to the DDCMP controller. The M68000 core
should not write to any fields of this BD after it sets this bit. Note that the empty bit
will remain set while the DDCMP controller is currently filling the buffer with re-
ceived data.
controller places incoming data into the first BD in the table.
been closed by the DDCMP controller, which can cause interrupts.
The user is required to set the wrap bit in one of the first eight
BDs; otherwise, errant behavior may occur.
To correctly identify buffers containing headers, the buffer size
should be eight or more bytes in length so that the header will fit
in a single buffer.
MC68302 USER’S MANUAL
NOTE
NOTE
MOTOROLA