KYOWA WGA-910A Series Instruction Manual page 24

2) Setting the external device
Set external devices by conforming to signal specifications of the WGA-910A.
RS-485 transceiver of the WGA-910A is provided with fail safe function that is designed to have the CPU
output (RO) becomes 1 (Hi) when signal is received and when between [+ (noninverting A)] and [-
(noninverting B)] is short-circuited or in float state.
In addition, when the WGA-910A is waiting to receive the signal, between A and B becomes nearly
short-circuited. And if transceiver of the external device does not have fail safe function, the output of the CPU
side may not become (Hi).
As a result, data transmitted from the WGA-910A may not be properly received. Therefore, it is recommended
to use the transceiver with the fail safe function.
The WGA-910A side: RS-485 circuit
Logical Table
[Sending]
/RE
0
0
X
[Receiving]
INPUT
/RE
0
0
0
0
INPUT
DE DI
1 1
1 0
0 X
A-B
DE
0 ≧200 mV
0 ≦-200 mV
0 OPEN
0 SHORT
OUTPUT
B A
0 1
1 0
Hi-Z Hi-Z
OUTPUT
RO
1
0
1
1
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