Helmholz 700-651-CAN01, Руководство пользователя

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Byte 0
15 14 13 12 11 10 9 8
Data length RTR unused
Byte 1 Byte 2
15 14 8 12 11 10 9 8 7 6 5 4 3 2 1 0
unused High Word CAN identifier (13 bits)
Byte 3 Byte 4
15 14 8 12 11 10 9 8 7 6 5 4 3 2 1 0
Low Word CAN identifier (16 bits)
The receipt of a new frame is recognized by the inversion of bit 0
in byte 0 of the
HANDSHK_IN area.
Once the message has been processed by the PLC program this
must be acknowledged to the DP/CAN coupler. Acknowledgment
is processed by the
RecObjecCmd byte.
5.4.3 Receive Object Service
Here again all bits must be used as toggle bits, i.e. the function is
executed when the bit is inverted.
Bit Function ReceiveObjCmd
0 Acknowledge last Receive Object frame
1 reserved
2 Delete RecObjStatus Overflow error bit
3 Reset Receive Object FIFO
4 reserved
5 reserved
6 reserved
7 reserved
A FIFO which can accept up to 24 messages has been
implemented in the DP/CAN coupler for the Receive Object. If
more than 24 messages are received without being fetched by the
PLC program, the oldest frames are removed and an overflow
error is displayed in the
RecObjStatus byte. The bits of the
ReceiveObjStatus byte must be processed as status displays.
Bit Function ReceiveObjStatus
0 FIFI Ok
1 Overflow occurred during last Receive
2 Overflow error flag
3
4 Number of frames still
5 in FIFO
6
7
Bit 2 of the RecObjStatus can be reset with bit 2 in the
RecObjCmd.
DP/CAN Coupler 23