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Table 52 Buffer Status Section of the CNSTAT Register
ST3 (DIR)
ST2
ST1
0
0
0
0
0
0
0
0
0
1
0
1
0
1
0
1
1
0
1
0
1
1
1
1
1
0
1
0
1
1
1
1
ST0 (BUSY)
0
0
0
1
1
0
1
1
0
0
0
1
1
0
1
1
0
0
0
1
0
0
0
1
1
0
1
1
1
0
1
1
Buffer Status
RX_NOT_ACTIVE
Reserved for RX_BUSY. (This condition indicates that soft-
ware wrote RX_NOT_ACTIVE to a buffer when the data
copy process is still active.)
RX_READY
RX_BUSY0 (Indicates data is being copied for the first time
→
RX_READY
RX_BUSY0.)
RX_FULL
RX_BUSY1 (Indicates data is being copied for the second
→
time RX_FULL
RX_BUSY1.)
RX_OVERRUN
RX_BUSY2 (Indicates data is being copied for the third or
subsequent times RX_OVERRUN
TX_NOT_ACTIVE
Reserved for TX_BUSY. (This state indicates that software
wrote TX_NOT_ACTIVE to a transmit buffer which is sched-
uled for transmission or is currently transmitting.)
TX_ONCE
TX_BUSY0 (Indicates that a buffer is scheduled for trans-
mission or is actively transmitting; it can be due to one of
two cases: a message is pending for transmission or is cur-
rently transmitting, or an automated answer is pending for
transmission or is currently transmitting.)
TX_RTR (Automatic response to a remote frame.)
Reserved for TX_BUSY1. (This condition does not occur.)
TX_ONCE_RTR (Changes to TX_RTR after transmission.)
TX_BUSY2 (Indicates that a buffer is scheduled for trans-
mission or is actively transmitting; it can be due to one of
two cases: a message is pending for transmission or is cur-
rently transmitting, or an automated answer is pending for
transmission or is currently transmitting.)
129
→
RX_BUSY2.)
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