Chapter 10 DeviceNet Communication Module AH10DNET
10-17
○
1
represents the control data that DeviceNet master sends and these data will be updated in the
registers starting from D1000 in real time. Meanwhile, ○
2
represents the values in the registers
starting from D500 and these values will be transmitted back to DeviceNet master automatically.
The two groups of data will be both updated in every scan period so as to achieve the real-time
control.
10.5 Bit-strobe Command
10.5.1 Bit-strobe Work Principle
Bit-strobe is one of the DeviceNet standard I/O transmission methods. The command length is fixed
to 8 bytes, i.e. 64 bits. (Maximum 64 stations exist on the DeviceNet network.) And one bit
corresponds to one node. In the bit-strobe transmission method, the master does not send the
control data to the slave. But when the corresponding bit is set to OFF, the slave needs to reply the
I/O data to the master; when the corresponding bit is set to ON, the slave does not need to reply the
I/O data to the master.
If the starting address for the output is D500, the corresponding relations between bit-strobe
registers and the nodes are shown as the following table.
Bit-strobe
register
Corresponding network node
Note:
1. If the starting address for the output is set to D123 (which you can refer to section 10.6.2), the
bit-strobe registers are D123~D126 instead of D500~D503.
2. If the slave does not support the bit-strobe function, the slave will still reply the I/O message to
the master after the corresponding bit is set to ON.
b0b1b17 b15 b14b30
b2b18
... ...... ...
b16b31
D501
Node 0
Node 1
Node 2
Node 14
D500
... ...
Suppose the starting address for the output is D500 and the slaves support the bit-strobe function.
When bit 0 in D500 is OFF, the node 0 is selected and it needs to return its data to the master. When
bit 0 and bit 1 are both OFF in D500, the node 0 and node 1 are both selected and they need to
send their own data to the master.
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