Motorola MC68302 User Manual page 149

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X - External Buffer
1 =The buffer associated with this BD is in external memory.
0 =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 CP will receive incoming data into the first BD in the table, allowing
the user to use fewer than eight BDs to conserve internal RAM.
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 will be interrupted when this buffer has been com-
pletely filled by the CP, indicating the need for the M68000 core to
process the buffer.
0 =No interrupt is generated after this buffer has been filled.
The following bits contain status information written by the CP after it has
finished receiving data in the associated data buffer.
C - Control Character
1 =This buffer contains a user-defined control character in the last byte
location.
0 =This buffer does not contain a control character.
A-Address
1 =When working in nonautomatic multidrop mode, this bit indicates
that the first byte of this buffer contains an address byte. The address
comparison should be implemented in software. In automatic multi-
drop mode, this bit indicates that the BD contains a message received
immediately following an address recognized in UADDR1 or UADDR2.
This address is not written into the receive buffer.
O=The buffer contains data only.
M -Address Match
This bit is meaningful only if the A bit (bit 10) is set and the AUTO bit is
set in the UART mode register. Following an address match, this bit defines
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