System Description
At the heart of the system is the DMux Control Unit (DCU) which is a microprocessor based controller. Within its RAM memory is maintained the state of each display point. Each individual point can be in one of the following states: OFF, ON, FLASH, BLINK, DIM, or MODULATE. The DCU updates every point on the display board 240 times a second thereby achieving each of these effects.
The DCU interfaces to the display points via the Distributed Multiplexer (DMux) Output Boards. A 26-conductor ribbon cable is used to daisy chain up to 32 DMux boards and connect them to the DCU. Each DMux output board has 64 drivers thus allowing control of up to 2048 output points on a single ribbon cable. The ribbon cable can be up to 500 feet long with proper termination. The DCU can be expanded to control up to eight such cables.
Different model DMux output boards are available with various output drive capabilities. Each DMux board has a 5-position dipswitch, which selects a unique address for each board on the bus. In 2048 or 4095 point systems the DCU updates the output latches on up to 64 DMux boards 240 times a second. In 16,384 point systems up to 256 DMux boards are refreshed 4 times a second.
Display lamps or LED’s connect via twisted wire pairs to 64 connectors on the DMux output board. An alternate scheme allows connecting of dual points via 32 connectors using 3-conductor wire. The lamp power supply voltage is connected to the DMux output via a single terminal block and is internally distributed on the board to all output connectors.
The DMux output boards require +5 volt DC power for their operation. This power is bused from one or more power supplies to a terminal block on the DMux board. The number of logic power supplies used depends on the size of the system and the distribution of the DMux boards. Voltage sense leads from each DMux logic power supply (up to four) are brought to the DCU where they are monitored for possible outage. Similarly, dry relay contacts brought from each lamp power supply (up to four) are sensed by the DCU. The wiring must be such that the contact is closed when the power supply is operational and opens when it fails.
The DCU accepts commands from a remote keyboard/display or from one or more supervisory computers (via serial or parallel interfaces). The commands are for the changing the state of any or all display points, that is for placing a point into OFF, ON, FLASHING, BLINKING, DIMMED or MODULATING state. Thus the supervisory computer needs only to command when a display point changes state and not for every flash or blink of a point. The DCU can also be commanded to return the current status of a display point (as kept in its memory). In addition the DCU can be commanded to return the current system status showing the state of the DCU software, DCU hardware, and system power supplies.
The DCU has "operating" and "test" modes as selected by the front panel key switch. The key switch positions operate as follows:
RESET Computer is reset and all display points are OFF.
RUN/LOCK Control of display points is via host interface.
MANUAL Control of display points is via Keyboard/Display.
TEST Diagnostic and configuration mode.
A remote keyboard/display is provided with the DCU for MANUAL mode and TEST mode operation. The keyboard consists of a set of hexadecimal keys, 6 function keys, and 6 control keys. The display is a 2 line by 24-character LCD alphanumeric display. In MANUAL mode all display points can be controlled via the keyboard/display. In TEST mode all diagnostics and utility programs are controlled via the keyboard/display. The keyboard/display unit is designed for either tabletop or hand-held use. It is connected to the DCU via standard modular telephone connectors and cable. This cable can be up to 200 feet long which allows the unit to be operated within the entire perimeter of the display board.
Three RS232C serial interfaces are an integral part of the DCU. Each interface is configurable via the keyboard/display for baud rate, data bits, parity, or stop bits. In RUN/LOCK mode the interfaces allow a supervisory computer to control the display points. Connection to the interfaces is via 9 pin female "D" connectors configured for DTE operation.
An I/O extender connector is provided with the DCU to allow expanding the number of control interfaces of the DCU. A DMux bus expansion module is available which provides eight DMux bus connectors for controlling up to 16,384 points. The DIM and MODULATE functions will not operate with this module. A parallel interface expansion module is also available which provides up to two 16 bit full duplex parallel interfaces.
A power fail option is offered which incorporates battery backed RAM memories which have a data retention capability which exceeds ten years. With this option installed, the DCU will retain point status during a power failure.
At the heart of the system is the DMux Control Unit (DCU) which is a microprocessor based controller. Within its RAM memory is maintained the state of each display point. Each individual point can be in one of the following states: OFF, ON, FLASH, BLINK, DIM, or MODULATE. The DCU updates every point on the display board 240 times a second thereby achieving each of these effects.
The DCU interfaces to the display points via the Distributed Multiplexer (DMux) Output Boards. A 26-conductor ribbon cable is used to daisy chain up to 32 DMux boards and connect them to the DCU. Each DMux output board has 64 drivers thus allowing control of up to 2048 output points on a single ribbon cable. The ribbon cable can be up to 500 feet long with proper termination. The DCU can be expanded to control up to eight such cables.
Different model DMux output boards are available with various output drive capabilities. Each DMux board has a 5-position dipswitch, which selects a unique address for each board on the bus. In 2048 or 4095 point systems the DCU updates the output latches on up to 64 DMux boards 240 times a second. In 16,384 point systems up to 256 DMux boards are refreshed 4 times a second.
Display lamps or LED’s connect via twisted wire pairs to 64 connectors on the DMux output board. An alternate scheme allows connecting of dual points via 32 connectors using 3-conductor wire. The lamp power supply voltage is connected to the DMux output via a single terminal block and is internally distributed on the board to all output connectors.
The DMux output boards require +5 volt DC power for their operation. This power is bused from one or more power supplies to a terminal block on the DMux board. The number of logic power supplies used depends on the size of the system and the distribution of the DMux boards. Voltage sense leads from each DMux logic power supply (up to four) are brought to the DCU where they are monitored for possible outage. Similarly, dry relay contacts brought from each lamp power supply (up to four) are sensed by the DCU. The wiring must be such that the contact is closed when the power supply is operational and opens when it fails.
The DCU accepts commands from a remote keyboard/display or from one or more supervisory computers (via serial or parallel interfaces). The commands are for the changing the state of any or all display points, that is for placing a point into OFF, ON, FLASHING, BLINKING, DIMMED or MODULATING state. Thus the supervisory computer needs only to command when a display point changes state and not for every flash or blink of a point. The DCU can also be commanded to return the current status of a display point (as kept in its memory). In addition the DCU can be commanded to return the current system status showing the state of the DCU software, DCU hardware, and system power supplies.
The DCU has "operating" and "test" modes as selected by the front panel key switch. The key switch positions operate as follows:
RESET Computer is reset and all display points are OFF.
RUN/LOCK Control of display points is via host interface.
MANUAL Control of display points is via Keyboard/Display.
TEST Diagnostic and configuration mode.
A remote keyboard/display is provided with the DCU for MANUAL mode and TEST mode operation. The keyboard consists of a set of hexadecimal keys, 6 function keys, and 6 control keys. The display is a 2 line by 24-character LCD alphanumeric display. In MANUAL mode all display points can be controlled via the keyboard/display. In TEST mode all diagnostics and utility programs are controlled via the keyboard/display. The keyboard/display unit is designed for either tabletop or hand-held use. It is connected to the DCU via standard modular telephone connectors and cable. This cable can be up to 200 feet long which allows the unit to be operated within the entire perimeter of the display board.
Three RS232C serial interfaces are an integral part of the DCU. Each interface is configurable via the keyboard/display for baud rate, data bits, parity, or stop bits. In RUN/LOCK mode the interfaces allow a supervisory computer to control the display points. Connection to the interfaces is via 9 pin female "D" connectors configured for DTE operation.
An I/O extender connector is provided with the DCU to allow expanding the number of control interfaces of the DCU. A DMux bus expansion module is available which provides eight DMux bus connectors for controlling up to 16,384 points. The DIM and MODULATE functions will not operate with this module. A parallel interface expansion module is also available which provides up to two 16 bit full duplex parallel interfaces.
A power fail option is offered which incorporates battery backed RAM memories which have a data retention capability which exceeds ten years. With this option installed, the DCU will retain point status during a power failure.