GarettCom 5843HRT User Manual page 21

Models 5843, 5844, 5843S and 5844S
RS232 or TTL
The communication logic and control software of the Master IED must be able to manage the receipt of its
echoed request. The receipt of the echo can be used in conjunction with a watchdog timer to continuously
verify loop integrity.
When addressed, the Slave will transmit an appropriate response. Each Link/Repeater connected to a Slave
IED must have its Repeat Switch set in the "ON" position. In this mode, all signals received on a Slave's R
optical port are delivered to the IED's communication port and at the same time repeated out the T optical port
to the next device in the loop.
Link/Repeater transmits the IED's response out the T optical port. The response is repeated at each Slave
device, until it arrives at the Master.
When an IED is a Slave, it should not attempt to initiate a transmission while it is receiving a signal. Since
signals being received are also being repeated at the same time, any attempts to transmit its response while
still receiving can corrupt both transmissions due to a data collision.
In Master/Slave Loop Operation, half duplex communication (sequential transmit and receive functions) is
available. Only the Master can communicate full duplex (simultaneous transmit and receive) in a Master/Slave
loop.
In a Master/Slave Loop Operation, the communication logic (control software) and the Master IED must
manage:
1) The transmission to Slaves (including addressing).
2) The receipt of the echo of its transmissions.
3) The receipt of the Slave's response to its transmission.
4) The control of the Slaves to prevent the initiation of a transmission while receiving a signal.
2.2.1 Installation
1. Set the DTE/DCE Switch to the appropriate position for each Link/Repeater and its respective IED.
2. Set the Repeat Switch to the "OFF" position on the Master. Set the Repeat Switch to the "ON"
position on each Slave.
3. Connect the Link/Repeater to the IED's RS-232 or TTL communication port (Including any adapter
that may be needed).
4. Connect the Fiber Optic Cables (T of one device to R of the next device in the loop). Continue
around the loop back to the Master to close the loop.
If an IED determines that this request requires a response, then the
If a Slave IED attempts to transmit while receiving a message, a
data collision will occur.
APPLICATION NOTE
NOTE
CAUTION
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