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4-100
. I - Interrupt
1 =The M68000 core will be interrupted when this. buffer has been serv-
iced by the DDCMP controller.
0 =No interrupt is generated after this buffer has been serviced.
L- Last
1 =The last bit is set by the processor to indicate that this buffer is the
last buffer in the current message.
O=This buffer is not the last in the message.
NOTE
The DDCMP controller checks the TC bit, not the last bit, to determine
whether to append the CRC sequence. The DDCMP controller will
transmit the programmable number of SYN1-SYN2 pairs before
transmitting the next buffer (message) when the last bit is set.
TC-Tx CRC
1 =Transmit a CRC16 sequence after the buffer's last data byte .
0 =Do not transmit a CRC sequence after the buffer's last data byte.
When the last bit is not set but TC is set, the DDCMP controller will
append the next buffer immediately following the CRC sequence. The
preset value for the CRC16 calculation is located in the PCRC register
and should be initialized to all zeros or all ones.
Bits 9-2 - Reserved for future use.
The following status bits are written by the DDCMP controller after it has
finished transmitting the associated data buffer.
UN - Underrun
The DDCMP controller encountered a transmitter underrun condition while
transmitting the associated data buffer.
NOTE
This error can occur only on synchronous links.
CT-CTS Lost
CTS in NMSI mode or grant in IDL/GCI mode was lost during message
transmission.
MC68302 USER'S MANUAL
MOTOROLA
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