Unit installation

RSU-503 Redundancy Switch Unit Theory of Operation
Rev. 8 3–3
Although the switch M&C is considered to be the slave unit on the MTI RS-232 bus, it
becomes the master when communicating to each of the two RFTs.
When not servicing MTI requests, the M&C monitors indicators, faults, and voltages.
When applicable, it generates switch-over pulses.
When polled from the MTI, the switch M&C will perform the following functions:
1. Return a response acknowledging receipt of the command.
2. Decode the address in the message, compare it to the stored addresses, and route
it to its intended destination.
3. Return a block of status information when requested.
3.4.2 Switch Indicators
Address 9000 reads in the eight indicator bits representing the four uplink and four
downlink indicator positions. The following tables show how the four bits are decoded to
indicate whether the unit A or B is currently online.
Uplink
B0 B1 B2 B3 WR8000, B0 WR8000, B4
IF_A RF_A IF_B RF_B 1 = A ON LINE
0 = B ON LINE
1 = OKAY
0 = AMBIGUITY FAULT
0000 1 0
0001 1 0
0010 1 0
0 0 1 1 1 1 - Valid state, A online
0100 0 0
0101 0 0
0110 0 0
0111 0 0
1000 1 0
1001 1 0
1010 1 0
1011 1 0
1 1 0 0 0 1 - Valid state, B online
1101 0 0
1110 0 0
1111 0 0