Data Link Controller Interface
1. Each function unit in the example IRON control structure will use data links for internal and external communication, meaning on connections to all places with which they will need to exchange data. That link is usually called an interface and is designed here as a Data Link Controller. It's job is to ensure that the integrity of data on the I/O lines are technically correct, before that data is passed on as being valid. One could call this electronic paper or documentation. It can coexist together with hand delivered paper.
2. I/O represent the outside world. It is bidirectional, therefore it can be constructed as two individual single connection or as channels on a single connection. Two individual single connections makes transmission error detection easy.
3. The function block that contains the letters R, G and B are optical couplers that provide electrically isolated links to the outside world. The connections from the outside world are of the same type. They are not shown in the drawing. That means that light will be transmitted and received at the information exchange level being discussed here.
4. The red circles A, B and C represent computing units. In this type of application, they should not be in close physical immediate areas to each other.
5. The computing units A, B and C are also connected to each other so that they can communicate with each other internally.
6. Only one of the computing units will be active on line at any given time. That means able to send.
7. Each computing unit, as indicated in the drawing, is assigned a light color on which it can send. The receive sides will be able to decode all the available colors.
8. The idea here is that:
A. The computing units A, B and C will internally check and record data that is to be transmitted.
B. When the data arrives at the I/O point, they will all three read that data on the receive connection and there by be able to see, if the data that is going out really is digitally correct.
C. Data that is coming in from a distant source is decoded and then the three computing units will pass the received results to each other for comparison and storage.
D. If there is a problem on the transmit or receive side, the problem can be localized instantly. That means that this data link controller can check itself.
E. This data checking is NOT for judicial purposes.
9. This is also a further opportunity to setup an electronics technology industry in Africa, because if the circuit is to be implemented correctly, each computing unit in the picture will need SIX separate communication lines so that errors such as, which unit has developed a defect can be analysed by the construction itself and thereby return singular results than will be the input to it's built in decision logic units. The result is that the system checks it's own activity for errors and people will check their own activity for errors. Each arrow head represents a connection line.
10. 6 connection lines to the outside world and 6 internal connection lines, means that each group of connections can take on a maximum of 64 states. Those amounts are low enough to allow real time software driven error detection and decision making. The system can be designed to find an hardware error that is qualified by using the time when it occurs and relate it to a source. For internal checking, the system relies on the detection of the first error. There are no higher priority objects in this system, only majority logic.
11. The result is that new hardware will be required and they can be the basis for an African electronics industry.
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