The Microlok II system is a multi-purpose monitoring and control system designed for railway and transit applications. It employs diversity and self-checking concepts to ensure fail-safe operation, performing critical operations in diverse ways using diverse software and testing hardware with self-checking operations. Permissive outputs are only allowed if diverse logic operations correspond and self-checks reveal no failures. The system combines vital and non-vital hardware with executive software that processes site-specific application logic tables using dual-path processing and double storage techniques, along with continuous hardware monitoring through extensive built-in diagnostics. Any failure in a critical component results in the system returning to a safe state.
Function Description
The Microlok II interlocking system performs several key functions:
- Control Relays: Drives signal, point, crank handle, LC gate, and siding control relays.
- Monitoring: Monitors point position, track circuit occupancy, and other field inputs.
- Vital CPU: Serves as the central vital CPU for overall system monitoring, control, diagnostics, and data recording.
- Logic Execution: Executes executive and application logic for vital interlocking functions, as well as non-vital control panel and operator VDU functions.
- Serial I/O: Provides serial I/O channels for communication between Microlok II units, with CAB/other non-vital applications, and for maintenance and diagnostic functions.
Hardware Overview
The Microlok II system consists of modular card file-mounted equipment and external peripheral devices that interface the card file circuitry to field equipment and other control systems.
- Environmental: Operates in a standard railway environment with ambient temperatures ranging from -40°C to +70°C and 0-95% non-condensing humidity. It meets specified EMI and vibration requirements.
- Physical: The card file is 16.75 inches wide and can be mounted in a standard 19-inch rack. Boards feature faceplates for status display, with blank panels available for empty slots. The system accepts external battery power from 9.8V DC to 16.2V DC, converting it to required internal voltages. A start-up voltage requirement of 11.5V DC prevents recovery when battery voltage is low. Nominal 24V input/output boards operate within a 19.6V DC to 32.4V DC supply range.
- Cardfile: A G64/96 bus-based card file designed to house standard 6UX220 Euro card plug-in printed circuit boards. It has twenty slots:
- Slots 1-15 & 20: Accommodate non-vital or vital I/O boards.
- Slots 16 & 17: Reserved for the Power Supply board.
- Slots 18 & 19: Reserved for the CPU board.
- CPU Board: Controlled by a Motorola 68332 microprocessor operating at 21 MHz, with 2KB of internal fast termination RAM. Most internal operations are 32 bits wide, while external bus cycles are 16 or 8 bits wide. Executive and application software are stored in four flash EPROMs (up to 8MB). Flash EPROMs allow direct handling of software via a PC connected to the front panel serial port. Jumpers enable/disable flash EPROMs for programming. The CPU connector housing includes an internal EEPROM for site-specific configuration data, ensuring data integrity even if the CPU board is replaced.
- CPU Functionality:
- Monitors external inputs from vital and non-vital input boards.
- Processes vital external inputs and executes application logic.
- Drives vital output boards as required.
- Monitors and controls serial communication ports.
- Tests individual vital input and output channels for faults.
- Monitors system internal operation for faults.
- Controls power to vital outputs via the card file power supply and an external VCOR.
- Records system faults and routine events.
- Responds to CPU board front panel switch inputs and operates displays.
- Interacts with a laptop PC for diagnostics, programming, and software upgrades.
- Serial Data Ports: Provides five serial data ports:
- Ports 1 & 2: RS-485 hardware interface.
- Port 3: RS-423 & RS-232 interface.
- Ports 4 & 5: RS-232 interface.
- Power Supply Board: A double-width board operating from 9.5V to 16.5V DC, producing 5V at 3A and +12V at 1A for card file circuitry. Requires 11.5V DC for start-up.
- Functions:
- Converts external supply voltage (9.8V to 16.2V DC) to regulated +12V and +5V for internal circuits.
- Supplies energy to the VCOR relay coil under CPU control.
- Vital Role: Essential for the fail-safe design, distributing regulated +12V and +5V power to all boards via the backplane bus.
- Physical I/O: Characteristics chosen to accommodate standard railway and transit interface devices, including 24V DC battery supply, vital and non-vital relays, lamps, and LED indications. Voltage and current limits are based on device requirements.
- Non-Vital I/O Board (NV.IN32.OUT32): Receives non-vital inputs (controls) and generates non-vital outputs (indications). Connects 32 inputs and outputs to a 96-pin connector. Employs polyswitches for output circuit protection (auto circuit breaker at ~0.75A). Inputs are activated from 6V DC to 30V DC.
- Minimum ON threshold for Non-Vital Input: 4.5V DC (nominal 24V DC systems).
- Maximum OFF threshold for Non-Vital Input: 2V DC (nominal 24V DC systems).
- Vital Output Board: Controls outputs via "high side" software-controlled switches. Loads connect from outputs to battery negative. Each output is protected by a polyswitch. A short to battery (-) trips the polyswitch and causes the VCOR relay to drop. A short to battery (+) is equivalent to a false output, causing the VCOR relay to drop.
- Each board has 16 outputs, assigned to final relays driving outdoor signaling gears (e.g., HR, DR for signals; WNR, WRR for points).
- CPU continuously monitors output boards; abnormal voltage leads to system reset/shutdown.
- Minimum ON voltage for Vital Output: 95% of I/O supply battery (24V DC outputs).
- Maximum OFF voltage for Vital Output: 1.5V DC (24V DC output).
- Output load capability: Minimum 100Ω for 24V DC outputs.
- Vital Input Board: No power connections through the upper connector. Signal battery can activate inputs when wiring to a relay contact circuit within the same Microlok II house. Isolated source used for circuits outside the house.
- Each board has 16 inputs, assigned to detect outdoor gear status (e.g., ECRs for signals, WKR for points, TPR for track).
- Normally configured with double cutting arrangement for outdoor gear detection.
- Minimum ON threshold for inputs: 19.6V DC (24V DC inputs).
- Maximum OFF threshold for inputs: 9.0V DC (24V DC inputs).
- Vital Cut-Off Relay (VCOR): Contacts control power to all card file vital outputs. Controlled by the CPU board. CPU performs continuous diagnostics; failure of a safety-critical diagnostic commands the CPS on the power supply board to remove DC supply to the VCOR coil, opening contacts and defaulting interlocking equipment to the most restrictive state. Uses a PN-150B vital biased relay.
- Address Select PCB: Jumpers determine board addressing, automatically set by the compiler after application program compilation. Ensures the correct board type is used in each slot as defined in the application logic.
- Each PCB has 6 jumpers.
- Each slot has a unique jumper setting.
- 48-pin PCBs for vital boards, 96-pin PCBs for non-vital boards.
- Keying Plug: Each card file slot has a 12-way female keying guide to ensure proper board installation. Boards have corresponding male guides with specific keying tab patterns. Keying plugs can be removed to change board types.
Serial I/O
The system supports RS-232, RS-423, and RS-485 active ports for application interface processing. All ports provide Transmit (TXD), Receive (RXD), Request To Send (RTS), and Data Carrier Detect (DCD) signals. At least one port provides a Clear To Send (CTS) control input. Control lines are accessible for modification of electrical properties without PCB modification.
- Microlok Protocol: Supports 1 to 32 Serial Stations per link, with addresses 1-127. Handles 0-128 input and output Boolean bits. Stale Data Time-Out (SDTO) range: 0.100 to 25.000 seconds. Polling Interval Timer range: 0 to 2.000 seconds. No-Response Timer range: 30 to 5000 milliseconds. Less restrictive inputs (1 state) asserted after two consecutive messages; more restrictive inputs (0 state) asserted after one message. Restrictive outputs are latched and transmitted until acknowledged.
- Genisys Protocol: Non-vital protocol supporting 1 to 32 Serial Stations per link, with addresses 1-255. Handles 0-512 input and output Boolean bits. SDTO range: 1 to 600 seconds. Polling Interval Timer range: 0 to 2.000 seconds. No-Response Timer range: 30 to 25000 milliseconds.
Software
The Microlok II software comprises executive software (operating system) and application-specific user-written software, along with self-checking diagnostics.
- Executive Software: US&S developed, standard for all Microlok II systems. Responsible for overall vital monitoring and control, including vital input monitoring, decision-making for interlocking functions, monitoring I/O channels, processing user inputs, internal/external diagnostics, event/error recording, serial data port management, and application program execution.
- Application Software: User-developed, application-specific logic for the Microlok II system. Compiled into data tables interpreted by executive software. Site-specific configuration data stored in Cardfile-mounted EEPROM, loadable via CPU front panel or Maintenance tools.
Vital Diagnostics
Processor activities for vital interlocking operations are continuously monitored by internal diagnostics within the Executive software. Microlok II uses diversity and self-checking. Permissive outputs require corresponding diverse logic operations and no self-check failures. Any critical equipment failure leads to a safe state. CPU board diagnostics control power to vital outputs via the CPS and VCOR. The CPS must continuously receive a 250Hz signal from the CPU; if the CPU detects an error or fails to generate this signal, DC power to the VCOR coil is removed, opening contacts and defaulting outputs to the most restrictive state.
System Operating Modes
The Microlok II controller supports various operating modes:
- Normal Mode: Default mode; all outputs and application processing active. All other system functions available.
- Selective Shutdown Mode: Entered when persistent Critical Errors prohibit complete system operations. All Vital Physical Outputs disabled. Other application processing (logic, serial links, vital inputs, non-vital I/O) continues.
- User Selective Shutdown Mode: Entered when identified by application logic as the operational mode, otherwise Normal Mode. All Vital Physical Outputs disabled. Other application processing continues.
- Complete Shutdown Mode: Entered when persistent Critical Errors prohibit system operations. No system I/O or logic processing performed; all vital outputs in most restrictive state. Diagnostic Interfaces function if possible.
- Reset Menu Mode: Unit remains in initialization routines. No system I/O or logic processing performed; all vital outputs in most restrictive state. Entered via Integral User Interface.
- Configuration Mode: Unit in special non-operational mode for Application Configuration. No system I/O or logic processing; all vital outputs in most restrictive state. Entered by Application Developer.
- Boot Mode: Allows Generic System Software and/or Application Image to be loaded. No other system activities. Entered by Application Developer.
Logic Processing
Boolean logic processing in Microlok II emulates relay logic. Supports table and block processing. Break-Before-Make execution of Boolean logic equations. All Boolean Variables used as operands are Logic Triggers, causing equation evaluation on state change. Supports traditional computer program-like logic processing, executing top-down when triggered. Logic blocks for numeric and Boolean processing operate top-down when triggered, only on 0->1 transitions of Logic Triggers.
System Logs
The Microlok II system logs and reports critical errors, warnings, and operational events. The Maintenance Tools provide four tools to review logged information.
- System Event Log: Records up to 5000 most recent critical errors, warnings, and events. Newest entries overwrite oldest when full.
- Critical error: System fault preventing normal operations (hardware, diagnostic, application logic failures).
- Warning: System fault/condition not affecting operational mode.
- Event: Informs user about system actions.
- System Error Log: Records up to 50 most recent critical system errors. Newest entries overwrite oldest when full.
- System User Data Log: Records user-specified events (state changes, date, time). Capable of recording up to 90,000 Boolean changes or 64,000 Boolean/numeric changes.
- System Merged Event Log: Views errors, warnings, and events like the System Event Log. Provides graphic displays of parameters and events specified in the User Data Log. Records all changes to parameters and events. Uses both text-based and graphic data displays.
- All recent critical errors, warnings, and events appear in text mode.
- All user-specified indications appear in graphic mode.
Important Technical Specifications
- CPU: Motorola MC68332, 21 MHz, 32-bit internal operations, 16/8-bit external bus.
- Memory: Up to 8MB Flash EPROMs (4M x 16), 128KB Fast Static RAM (2 banks of 64K x 16), 256KB Low Power Static RAM (4 banks of 512K x 16) with >4hrs battery backup at 25°C.
- Power Input: 9.5V to 16.5V DC (nominal 12V DC), 11.5V DC minimum start-up, 0.5V P-P maximum ripple.
- Cardfile Power Supply Outputs:
- +5V @ 3A for 5V internal circuits.
- +12V @ 1A, -12V @ 1A for 12V internal circuits.
- +12V into 400 ohm coil for VCOR.
- Non-Vital I/O (N17061501):
- Input/Output Voltage Range: 6.0 to 30.0V DC.
- Externally Available Inputs/Outputs: 32 each.
- Current Rating On Outputs: 0.25A (polyswitch-protected) for outputs 1-30; 5.0A fuse for outputs 31, 32 (suitable for lighting lamp up to 25W).
- Vital Output (N17060502):
- Voltage V_BATT Range: 24V.
- Load Resistance Range: 100Ω - ∞.
- Max. OFF Voltage: 1.5V.
- Min. ON Voltage: V_BATT - 1V.
- Vital Input (N17061002):
- Nom. Input Voltage: 24V.
- Min. Voltage to Ensure ON State: 16.0V.
- Voltage to Ensure OFF State: 12.0V or less.
- Max. Sustained Input Voltage: 62V.
- Mixed Vital I/O (N17061602):
- Output Specifications (same as Vital Output).
- Input Specifications (same as Vital Input).
- VCOR (US&S PN-150B N322500-701):
- Contacts: 6FB.
- Coil Resistance: 400 Ohms.
- Pickup Amps: 0.0132.
- Pickup DC Volts: 5.3.
- System Voltage: 10.
Usage Features
- User-Configurable Cardfile: Allows flexibility in board arrangement.
- Front Panel Interface: CPU board features alpha-numeric displays and LEDs for configuration programming menus, options, and status. Toggle switches (MENU L-R, MENU UP-DOWN, ADJUST UP-DOWN, ACTION ACCEPT-REJECT) provide user interaction.
- Diagnostic Link Connector (RS-232 DTE): DB9 connector for connecting to a Maintenance PC for system monitoring and diagnosis.
- Keying Plugs: Ensure correct board installation in card file slots, preventing misconfiguration.
Maintenance Features
- Flash EPROMs: Allow direct handling of executive and application software updates via a PC connection to the CPU board's front panel serial port.
- Internal EEPROM: Stores site-specific configuration data, which remains intact even if the CPU board is replaced, simplifying maintenance.
- Polyswitch Protection: Non-vital and vital output boards use polyswitches as auto circuit breakers, protecting output circuitry from overcurrents and shorts. They reset automatically when the fault is removed.
- Continuous Diagnostics: The CPU board performs continuous diagnostics on vital I/O channels and internal operations, ensuring fail-safe operation and detecting faults.
- System Logs: Comprehensive logging of critical errors, warnings, and operational events (System Event Log, System Error Log, System User Data Log, System Merged Event Log) aids in troubleshooting and historical analysis.
- Maintenance Tools Program: Used for inputting Executive software version upgrades and loading site-specific configuration data via a laptop PC.
- Reset Functionality: A momentary pushbutton on the CPU board resets the CPU and can place it in reset mode for maintenance.
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