Back to. Communication Products Group. Technical Notes. Local/Remote Control and Functional Description, 1:1 Redundant Switching Unit, One Rack Unit

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1 Back to Communication Products Group Technical Notes 25T008 Local/Remote Control and Functional Description, 1:1 Redundant Switching Unit, One Rack Unit

2 MITEQ TECHNICAL NOTE 25T008 MAY 1997 REV D LOCAL/REMOTE CONTROL AND FUNCTIONAL DESCRIPTION 1.O GENERAL DESCRIPTION 1:1 REDUNDANT SWITCHING UNIT ONE RACK UNIT The 1:1 Redundant Switchover Unit (RSU) is used with two converters, one On-line (Unit A) and the second in a Standby mode (Unit B). A fault condition in the On-line Unit A, or an operator generated command, will switch the Standby Unit B into the transmission path and remove Unit A from operation. The RSU is equipped with fully redundant power supplies and is available with remote bus interface options for off-line control and monitoring. Its design ensures continuous operation allowing a fault to be repaired and/or routine maintenance of a converter to be performed without disruption of signal transmission. 2.0 OPERATING MODES The operating modes are selected from the front panel or over the optional remote bus. 2.1 AUTO MODE In this mode the On-line/Standby status of Units A and B is automatically controlled by the RSU without operator intervention. The On-Line/Standby status of Units A and B (position of the transfer switch) is changed when a fault is detected from the On-line unit. Control of converter status is locked out from the front panel and the remote bus. 2.2 MANUAL MODE On-Line/Standby status of Units A and B is controlled from the front panel (LOCAL Mode) or the remote bus (REMOTE mode). Converter faults are still monitored by the RSU but have no effect on the On-Line/Standby status.

3 2.3 LOCAL MODE On-Line/Standby status and Auto/Manual mode may be selected from the front panel. Remote control is locked out, however, the RSU will still respond to monitoring commands. 2.4 REMOTE MODE On-Line/Standby status and Auto/Manual mode are selected from the remote bus. The front panel is locked out with the exception of the LOCAL/REMOTE switch. 3.0 FRONT PANEL The front panel is divided into four functional groups (Figure 1). 3.1 POWER Figure 1. Front Panel 1:1 RSU One Rack Unit AC power to the "A" and "B" redundant power supplies is selected with the PSA and PSB switches. 3.2 CONVERTER A/B, ON-LINE/STANDBY On-line/Standby status of each converter is indicated by the green and yellow LEDs. Pressing the On line/standby switch toggles the status of Unit A and Unit B if the RSU is in LOCAL/MANUAL mode. One unit is always on-line and the other on standby. 3.3 MODE The yellow LEDs indicate RSU mode. Pressing AUTO/MANUAL switches the RSU between AUTO and MANUAL (LOCAL mode only). Pressing LOCAL/REMOTE always switches the RSU between LOCAL and REMOTE mode. 2

4 3.4 ALARMS The red LEDs indicate a fault in Unit A, Unit B, Power Supply A, Power Supply B and the RSU. The RSU LED will turn on for the following conditions: Transfer switch in the wrong position Power supply fault RSU circuit board fault 4.0 REMOTE OPTIONS The RSU is available with several remote bus options, a remote Contact Closure option and a Local Only option. In all cases the RSU does not set the frequency of the converters. It is the responsibility of the system operator to manually or remotely set the frequency of each converter to the desired frequency. 4.1 LOCAL ONLY OPTION The RSU and converters are connected as shown in Figure 2. Since there is no remote bus, all RSU control is from the front panel. The LOCAL/REMOTE switch is disabled and the RSU will always remain in LOCAL mode. Figure 2. Local Only and Remote Contact Closure 4.2 REMOTE CONTACT CLOSURE OPTION The RSU and converters are connected as shown in Figure 2. Form C relay contacts are provided at the rear panel REMOTE connector and indicate RSU status, mode and alarm settings. When set to REMOTE mode, RSU status and AUTO/MANUAL mode may be set by momentarily or continuously shorting pins on the REMOTE connector (see REMOTE INTERFACE CONNECTOR). 3

5 4.3 REMOTE BUS OPTION In this configuration a System Controller is used to control the converters and RSU (see Figure 3). The Remote Bus options consist of several serial bus options (RS232/422/485) and the IEEE-488 bus option. SERIAL BUS - when polled the RSU will respond with Mode, Status or Fault Status information in either LOCAL or REMOTE mode. On-line/Standby status and AUTO/MANUAL mode are set from the System Controller only when the RSU is in REMOTE mode. IEEE-488 BUS - When addressed to talk, the RSU will respond with Mode and Status information in either LOCAL or REMOTE mode. When addressed to listen, the RSU will accept data only in REMOTE mode. Figure 3. Remote Bus Option 4

6 4.3.1 RS232/422/485 PROTOCOL All transmissions are multi-byte sequences beginning with a header byte and ending with a trailer byte and checksum byte. The transmitted bytes are all ASCII printable characters in the range of 20H to 7AH. Data transmission format is a 10 bit sequence consisting of 1 Start, 7 Data, 1 Parity and 1 Stop bit. Odd or Even parity is set from the rear panel ADDRESS DIP switch. All characters, including the checksum character, are checked for parity. If any character in the message has a parity, framing or overrun error, the entire message is ignored and no response is made by the converter. The RSU continually monitors the communications bus and will accept all messages addressed to it even when in LOCAL mode. When in LOCAL mode, receipt of any messages other than Fault Status, On-line/Standby Status and Mode will be ignored and the RSU will respond with an error code MESSAGE FORMAT The general message format is as follows: HEADER - DEVICE ADDRESS - COMMAND/ERROR CODE - PARAMETERS (if required) - TRAILER - CHECKSUM The response time from Message to acknowledge is 100 ms. maximum. Since all bytes are ASCII printable characters, a compatible terminal may be used to control the RSU or monitor traffic on the communication bus HEADER BYTE The Header Byte is 7BH, ASCII character "{" DEVICE ADDRESS BYTE The Device Address may take on the values from 40H to 5FH (32 possible addresses) COMMAND/ERROR CODES COMMAND CODES ASCII Code Character Function 50H, 3nH Pn Set On-line/Standby status 51H Q Return RSU/Converter Fault status 52H R Return RSU mode 53H S Return On-line/Standby status 55H U Set RSU mode 5

7 ERROR CODES ASCII Code Character Function 61H a Command not recognized 62H b Illegal parameter or parameter out of range 63H c RSU in Local Mode 64H d Busy PARAMETER BYTES Parameters are numeric characters. Non-numeric parameters such as ",", "." or values beyond the range of the RSU will be rejected and cause the RSU to respond with error code "b" TRAILER BYTE The Trailer byte is 7DH, ASCII character "}" CHECKSUM BYTE The Checksum byte is the sum modulo 95 of all message characters beginning with the header byte up to and including the trailer byte. The value 32 is subtracted from each character value before taking the modulo 95 sum. The value 32 is added to the final sum to obtain the Checksum value. All values are in decimal. Checksum = Mod [(Character Value - 32), 95] COMMAND CODES The following paragraphs describe each of the command codes SET ON-LINE/STANDBY STATUS: PA The RSU responds to the set command in Remote mode only. Remote Command Sequence: Pa RSU Response: P P = Command indicator a = 0 B On-line, A Standby a = 1 A On-line, B Standby 6

8 RETURN RSU/CONVERTER (UNITS A AND B) FAULT STATUS: Q The RSU responds in both Local and Remote mode. Remote Command: Q RSU Response: Qabc 0 = Normal 1 = Fault Q = Command indicator a = Unit A b = Unit B c = RSU RETURN RSU MODE: R The RSU responds in both Local and Remote mode. Remote Command: R RSU Response: Rab R = Command indicator a = 0 Remote a = 1 Local b = 0 Manual b = 1 Auto Return On-line/Standby Status: S The RSU responds in both Local and Remote mode. Remote Command: S RSU Response: Sa S = Command indicator a = 0 B On-line, A Standby a = 1 A On-line, B Standby 7

9 SET RSU MODE: UA The RSU responds to the set command in Remote mode only. Remote Command Sequence: Ua RSU Response: U U = Command indicator a = 0 Manual a = 1 Auto PROGRAMMING EXAMPLES The RSU address is 40H (ASCII code The following are typical commands and responses showing the ASCII printable characters. A. Set the RSU mode to AUTO. Controller Command {@U1}! RSU Response {@U}o B. Return the RSU/Converter Fault status. The response indicates a fault in the RSU. Controller Command {@Q}k RSU Response {@Q001}= C. Set the On-line/Standby status. The response indicates the RSU is in LOCAL mode and will ignore the command. Controller Command {@P1}{ RSU Response {@c}} DEVICE ADDRESS/BAUD RATE SELECTION The device address is set with the ADDRESS DIP switch on the rear panel. S1, 2, 3, 4 and 5 select the five LSBs of the address in binary (switch Off = "1", switch On = "0", S1 = LSB). The two MSBs are permanently set to "10" and not available to the user. The baud rate and parity are selected with switches S6, 7 and 8 in the following code (switch Off = "1", switch On = "0"). 8

10 S8 S7 Baud Rate S6 Parity 0 Even 1 Odd RS422 BUS TERMINATION (See Figure 4) A jumper selectable 120 ohm termination resistor is connected across the DATA IN +/- and DATA OUT +/- terminals. Installing E1 places the resistor across the DATA OUT terminals and E2 across the DATA IN terminals. Figure 4. RS422/485 Bus Termination Jumpers RS485 BUS TERMINATION (See Figure 4) A jumper selectable 120 ohm termination resistor is connected across the DATA +/ DATA - terminals. Installing E1 places the resistor across the terminals IEEE-488 CONTROL The RSU performs the basic Talker and Listener functions as specified in IEEE Standard 488. It is also capable of sending a Service Request to the IEEE-488 Controller and will respond with a status word when the Serial Poll Enable message is received DATA INPUT MESSAGE FORMAT The messages to and from the RSU are ASCII character strings terminated with CR, LF and EOI. 9

11 SET ON-LINE/STANDBY STATUS This message sets the on-line/standby configuration of Units A and B. The unit must be in MANUAL mode to respond to this command. Pa a = 0 B On-line, A Standby a = 1 A On-line, B Standby SET RSU MODE This message sets the RSU mode. Ua a = 0 Manual a = 1 Auto DATA FORMAT These messages determine the RSU s response when it is addressed to talk by the IEEE-488 Controller. A Data Format message remains in effect until another one is received. DQ is the power on default format RSU/CONVERTER FAULT STATUS FORMAT Data Format RSU Response DQ Qabc 0 = Normal 1 = Fault Q = Fault status format indicator a = Converter A b = Converter B c = RSU RSU MODE FORMAT Data Format RSU Response DR Rab R = Mode format indicator a: 0 = Remote, 1 = Local b: 0 = Manual, 1 = Automatic 10

12 CONVERTER ON-LINE/STANDBY STATUS FORMAT Data Format RSU Response DS Sa S = Converter on-line/standby status format indicator a: 0 = A Standby, B On-line 1 = A On-line, B Standby SERVICE REQUEST The RSU will issue a service request (activate the SRQ line) when a fault is detected in the RSU. The fault may be caused by a power supply problem, or transfer switch failure. The IEEE-488 Controller responds by sending the SPE message (Serial Poll) and addresses the RSU to talk. The RSU responds with the following message: Bit Number SRQ S1 S0 S0/1 indicates which component caused the service request by setting the appropriate bit to 1. S0 = Power Supply S1 = Transfer switch The bit 6 is 0 when service request is disabled. It only becomes 1 when SRQ is enabled and controller is reading the serial poll message the first time DEVICE ADDRESS/SERVICE REQUEST ENABLE The device address is set with the ADDRESS DIP switch on the rear panel. S1, 2, 3, 4 and 5 select the address assignment in binary (switch Off = "1", On = "0", S1 = LSB). Switch 8 enables the Service Request feature (switch Off = Disabled, On = Enabled). S6, 7 are spares. 11

13 5.0 NON-VOLATILE MEMORY With the exception of the Remote Contact Closure and Local Only options, the RSU stores all information in non-volatile memory. If power is lost momentarily or for a long period of time, the RSU will return to its original settings when power is restored. Option Remote Contact Closure Local Only Power On Settings REMOTE, AUTO AUTO REMOTE INTERFACE CONNECTOR RS232 - D subminiature connector, 25 conductor, male. J9-1 Ground -2 TX Data -3 RCV Data -4 RTS -5 CTS -7 Ground RS422 - Two D subminiature connectors, 9 conductor, female. J9-1 Ground -3 Data Out - -5 Data In - -7 Data Out + -9 Data In + J9A and B are internally connected together. RS485 - Two D subminiature connectors, 9 conductor, female. J9-1 Ground -3 Data - -7 Data + J9A and B are internally connected together. IEEE IEEE-488 compatible connector, 24 conductor, receptacle. Contact Closure - D subminiature connector, 25 conductor, female. Command (Input) Closed Common Open A On-line/B Standby B On-line/A Standby AUTO MANUAL Status, Mode, Alarms 12

14 (Output) Closed Common Open A On-line/B Standby B On-line/A Standby LOCAL REMOTE AUTO MANUAL RSU Normal RSU Fail Converter A Normal Converter A Fail Converter B Normal Converter B Fail Signal/Frame Ground 13 M:\TECHNOTE\25T008.DOC 13