National CP3BT26 - Manual (Page 129)

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CP3
BT26
Table 52 Buffer Status Section of the CNSTAT Register
ST3 (DIR) ST2 ST1 ST0 (BUSY) Buffer Status
0 0 0 0 RX_NOT_ACTIVE
0 0 0 1
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.)
0 0 1 0 RX_READY
0 0 1 1
RX_BUSY0 (Indicates data is being copied for the first time
RX_READY
→
RX_BUSY0.)
0 1 0 0 RX_FULL
0 1 0 1
RX_BUSY1 (Indicates data is being copied for the second
time RX_FULL
→
RX_BUSY1.)
0 1 1 0 RX_OVERRUN
0 1 1 1
RX_BUSY2 (Indicates data is being copied for the third or
subsequent times RX_OVERRUN
→
RX_BUSY2.)
1 0 0 0 TX_NOT_ACTIVE
1 0 0 1
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.)
1 1 0 0 TX_ONCE
1 1 0 1
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.)
1 0 1 0 TX_RTR (Automatic response to a remote frame.)
1 0 1 1 Reserved for TX_BUSY1. (This condition does not occur.)
1 1 1 0 TX_ONCE_RTR (Changes to TX_RTR after transmission.)
1 1 1 1
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.)