Detailed Description Central Heating Control System V10 (CHCSV10) As you might imagine this system would be quite complicated in reality. Where possible the description below attempts to simplify the system by stipulating assumptions and restricting scope.

Heating Duct There can be up to 20 ducts installed in the top of the range system. In our example only four are shown and you should model just four. A Heating Duct blows warm air that has been generated at the Heating Unit and blown through all duct pipes by the Heating Unit Fan. A duct may be open or closed and these states can be set either by CHCSV10 or manually. If a duct is closed manually it can only be reopened manually. This is to allow for situations where a duct has been deliberately closed to an area. When the central heating system is operational, the Heating Duct Controller reports on the current state of the duct on a pre-determined periodic basis (in our case we will say every five minutes). The CHCSV10 system determines if a new status has been found and if it has displays that information on the System Display.

Gas Meter Supply A Gas Meter is the connection point between the outside gas supply and the gas supply for the premises. There is in turn a connection supply from the Gas Meter to the Heating Unit where the gas is burnt to supply warm air to the premises and this is the external point we will refer to. Ordinarily, gas is always available and the meter simply records the number of cubic metres used (and the megajoule (MJ) equivalent). Sometimes the gas is not available due to maintenance or problems with supply. There may be circumstances where the gas is available but there is a need to stop gas being supplied to the Heating Unit. There may also be circumstances where the gas supply is stopped to the Heating Unit as well as the gas being unavailable. Therefore a Gas Meter Supply may be available or not available and stopped or flowing and these states can be set either by CHCSV10 or manually. When the central heating system is operational, the Gas Meter Supply Controller reports on the current state of the Gas Meter Supply on a pre-determined periodic basis (in our case we will say every 30 seconds). The CHCSV10 system determines if a new status has been found and if it has, displays that information on the System Display.

Heating Unit The Heating Unit supplies the warm air to the premises. The Heating Unit burns natural gas and a Heating Unit Fan circulates the warm air along the duct pipes and out of the ducts within the premises. There are a number of different units available with different burning and heating capacities. They all however contain the same functionality. A Heating Unit may be in a state of available or unavailable and operating or not-operating either through the functionality of CHCSV10 or by manual means. When the central heating system is operational, the Heating Unit Controller reports on the current state of the Heating Unit on a pre-determined periodic basis (in our case we will say every 30 seconds). The CHCSV10 system determines if a new status has been found and if it has, displays that information on the System Display.

Heating Unit Fan The Heating Unit Fan circulates warm air to the premises along the duct pipes and out of the ducts. There are a number of different units available with different circulation capacities. They all however contain the same functionality. A Heating Unit Fan in a state of available or unavailable and operating or not-operating either through the functionality of CHCSV10 or by manual means. In each case of a change of state, a message should be sent and displayed on the System Display signifying the new state. When the central heating system is operational, the Heating Unit Fan Controller reports on the current state of the Heating Unit Fan on a pre-determined periodic basis (in our case we will say every 30 seconds). The CHCSV10 system determines if a new status has been found and if it has, displays that information on the System Display. System Clock The System Clock designates the central heating systems date, time and day of week and is a vital component in the real time actions of the system. To make things a little easier we assume that the System Clock is always on (provided power is available or the system battery backup has available energy in the case of a power out). It is configured through the System Control Panel and its details are displayed on the System Display. The System Clock records time in seconds but time is only displayed in hours and minutes in either 24 hour time or am/pm format depending on configuration preferences. When the central heating system is operational, the System Clock sends the current time to the System Display on a pre-determined periodic basis (in our case we will say every 60 seconds). Additionally, every 24 hours at 12:00 midnight and whenever the system is powered up a request is made to the System Clock to provide the current date and day and these details are updated on the System Display. The day and time are used in conjunction with the temperature, heating programs and hardware availability to determine if the heating unit and fan should start.

System Temperature Detector The System Temperature Detector uses a negative temperature coefficient (NTC) thermistor and measures the ambient (room) temperature of the premises. It is another vital component in the real time actions of the system. Placement of the System Temperature Detector is important as it helps to determine when heating occurs. It is unusual not to have it co-located with the System Control Panel, System Clock and System Display. It is often a trade-off between convenience of location for those three components and the location where temperature best resembles the average temperature of the premises. To make things a little easier we assume that the System Temperature Detector is always on (provided power is available or the system battery backup has available energy in the case of a power out). It is configured through the System Control Panel and its details are displayed on the System Display. The temperature is recorded in Celsius or Fahrenheit depending on configuration preferences. When the central heating system is operational, the System Temperature Detector sends the current temperature to the System Display on a pre-determined periodic basis (in our case we will say every 60 seconds). This temperature is used to determine the operation of the heating unit based on the time, schedule and hardware availability.

System Display The System Display is responsible for communicating with the user of the system including as a configuration display, command confirmation display and as a real-time indicator of the status of the system. Configuration details include displays for setting the clock, choosing temperature settings and setting the heating programs (In your analysis it is not necessary to go down to the level of individual processes for each of these displays). There are many types of messages and command confirmations including those associated with shutting down/powering up the system, status messages for components and setting manual temperature overrides or resuming automatic heating.

System Control Panel This panel provides the interface that allows communication with the system. A pre-configured touch pad shows commands such as System Clock (Configure and Set Time), Configure Temperature Detector, Set Heating Program, Manually Change Heating, Resume Automatic Heating, Turn System Off and Turn System On. Configure the System Clock refers to setting the type of time reported. Set Time allows the system time to be changed. Configure Temperature Detector allows the user to select Celsius or Fahrenheit reporting of the temperature. Set Heating Program allows the user to set up the heating schedule for each day of the week. An example of a schedule for a day at the example factory might be: between 12:00:00am and 6:59:00am inclusive a temperature range of 50C to 100C should be maintained. That is, if the temperature, detected by the System Temperature Detector, falls below 50C during this time, the central heating system will turn on to heat the premises until an upper limit is reached e.g. 100C at which time the heating stops. between 7:00:00am and 5:59:00pm inclusive a temperature range of 150C to 200C should be maintained. between 6:00:00pm and 11:59:00pm a temperature range of 50C to 100C should be maintained. Manually Change Heating allows the user to set a temperature below which the temperature may not fall. No upper limit is specified. If a manual temperature is set then that overrides the automatic heating program until a new program is scheduled to begin at which time the heating program is in control unless a new Manually Change Heating selection is made. Resume Automatic Heating resets the system back to following the appropriate stored heating program/s.

Turn System Off will issue commands to close the Ducts, stop the Gas Supply (to the Heating Unit), stop operating the Heating Fan and Heating Unit if operating and set both these devices to unavailable. The System Display will be updated with a message to state that the central heating system is off and the new states of the Ducts, Gas Supply, Heating Fan and Heating Unit will also be reflected based on messages from their controllers.

Turn System On will issue commands to open Ducts (if they arent in a state of manually closed), start the Gas Supply and make the Heating Fan and Heating Unit available. The system will then follow normal automatic operations so that the temperature measured in combination with the program/s and hardware availability will control the heating of the premises.

Data Storage The CHCSV10 must be able to receive and store the data information received as detailed from each of the units above. However it is not necessary to have an historical record of events but rather there must be a set of information that allows the current status of the central heating system and its components to be determined and displayed. Thus it is important to have in some cases a previous value so that a comparison may be made to determine if the status of the system has changed and to act accordingly e.g. display changed information and/or change state/s of device/s. It is also important to have a set of configuration information that stores information on the System Clock and System Temperature Detector as well as the entered heating program/s.

CHCSV10 Operation Many of the operating features of CHCSV10 and the underlying hardware components have already been covered in preceding sections. Some additional information and rules follow. The peripheral components responsible for generating and circulating the heat the Ducts, Gas Meter Supply, Heating Unit Fan and Heating Unit largely follow the same set of processes i.e. periodically send a status (there may be more than one) that is then evaluated for availability for heating against the previous stored value, the new value is stored, displayed if necessary i.e. theres been a change and then further action may take place. With respect to the Ducts, each duct should be evaluated separately but there is a rule that the heating system cannot be turned on unless there are >= 50% of the total number of ducts open.

The automatic operation of the heating is dependent on the relationship between the room temperature and the appropriate program for the time and day of the week and the appropriate state of the heat generating and circulating components. Before heating can occur, the temperature measured by the System Temperature Detector must be evaluated against the temperature range stipulated in the appropriate heating program. If the temperature is below the minimum temperature of that range, a test of the appropriate status of all heat generating and circulating components is made and if these tests are met, the premises are heated. The heating continues until:

the temperature is measured to be above the range; or a status on one of the devices signifies that it is not able to participate in the heating; or the system responds to a Manually Change Heating command; or a Turn System Off command is selected.

Tasks to do :

1. An External Entity-Relationship Diagram (ERD) indicating relationships of the CHCSV10 and the other external entities in the system. You do not need to include attributes of the entities on the ERD, just the relationships and their cardinality and modality. 2. Data and Control Flow Diagrams (DFD/CFDs) - to sufficient detail that only a single task is carried out by each process at the lowest level (Do not however model the functionality of the System Clock - Configure and Set Time, Configure Temperature Detector, Set Heating Program processes; just have a process for each). You should show the control events/flows and data flows on the same diagrams. Use the real-time extensions for control flows etc shown in the lecture notes (slides 15-17 from week 3). You need to determine when and where events will occur. For example, whenever a piece of data becomes available it may need a control event to let the system know that it is available. These events must be clearly shown in these DFD/CFD diagrams and then handled in the CSPEC. 3. Process specifications (PSPECs) - a pseudo-code or similar design language specification is required for each process at the lowest level. A narrative description alone will not be considered sufficient. 4. Control Specifications (CSPECs) - use combinational or sequential FSMs as required, presented in an appropriate format. The idea is that the CSPEC will completely describe how each and every event or control flow is handled in the system. You need to provide both "Process Activation Table" and "State Machine Diagram" as appropriate. 5. A Data Dictionary is required to adequately describe each name or special term used in the analysis. This includes process names, data flow names, data stores, control flow names, control stores and events.

You should include sufficient detail to allow the system to handle all the monitoring and control aspects specified in the Detailed Description section of this document (and any further aspects you consider essential). If you think further information is required make reasonable assumptions and clearly state these in the submission