VME bus
VME bus computer standard, originally Motorola68000 series microprocessor. After that, it is used with many devices,IECPuttingANSI/IEEE 1014-1987. Attachment of Eurocard size is adopted physically, but signal connection is individual ones. 1981 first it is developed, is used widely even at today.
History
1979 year、 Motorola developed 68000 CPU. As for one Jack of the technicians Kister making the bus system where for 68000 systems are standardized VERSA busWith it called. After that, John Black to join, improving specification VERSA module With the product concept which is said was built up. Sven Rau of the Motorola European section and Max Loesel adding mechanical specification, tried to utilize Eurocard standard. As a result the fact that you complete to be the first VERSA bus -E, afterwards VME bus(VERSAMOdule EUrocard bus) With it was renamed (however Versa Module EuropaWith there is also a theory which is done).
After that, it reaches the point where many enterprises use this standard (Signetics, Philips, Thompson and Mostek etc.), directlyIECPuttingANSI/IEEE 1014-1987.
Standard of beginning was 16 bit bus. Is in order to store to the connector of existing Eurocard. But, after that passing the expansion of some time, the present time VME64 So there is 64 bit bus standard of the 6U card and 32 bit bus standard of the 3U card. Even in addition, hot swapping( plug and play) VME64x and the small card which are stipulated (IP) there is a mechanism, various connected standards and actualizes the link with the VME system a standard etc. which connect to the VME bus card.
In addition as for the VME bus, it was similar very wellVXI busIt was used even in development.
Details
The VME bus the pin which 68000 has that wayBackplaneIt is kind of something which is output. In many cases, the good design you cannot call this. Because the chip set which can use the bus is limited. (Really,ISA bus Intel. ) But, 68000 flat of 32 bits having memory model is feature,Memory segmentThose the way it is unrelated. As a result, VME although it is the design of 68000 winds, the design of 68000 reached the point where it is widely used because is widely used.
68000 and similarly VME the data and has 32 bit bus which address respectively is separated. As for 68000 itself address buses at 24 bits, as for the data bus they are 16 bits, but (inside 32/32), the designer had stared complete 32 bit mounting. Because it corresponds to both bus width, with VME two Eurocard connectors P1 and P2 are used. 32 these pins are triplex rows in P1, the address bus of 24 bits and the data bus and the other control signals etc. of 16 bits pass by this connector. There is a pin in one line already in P2, the remaining address 8 bit and the data 16 bit is set.
In order to control the bus, 9Arbitration bus(The arrange bus) is used. All communication was set to the busArbiter module(Arrange module) the card controls. As for the card when making request on the bus, Bus request in Slot number is sent with putting the line inside the arrange bus which is said in a low state. When arrange module releases the bus, you inspect those lines and you check whether there are no any which enter low state. If there is a line of low state Bus busySlot number of the card which notifies that the bus becomes busy state, with the line as low makes request Bus grant outIt outputs to the line.
The card which first makes request at this point in time obtains the use right of the bus. To write the data, address and the data are output to the bus,Address strobeLine and two Data strobeThe fact that the data is ready state with the line as low is shown, processing is executed with the entry line as low. Data strobe is two as for being, in order to appoint data size, due to the combination (with 8 bits, 16 bits, 32 bits, and VME64 furthermore 64 bits). The card which has the address which is appointed reads the data,Data transfer acknowledgeIt informs about completion, with the line as low if (or necessityBus errorLine). Also reading the data basically is the same, but the card first outputs just address on the bus, pulls the READ pin. The other card outputs the data of the address on the bus, pulls data strobe and shows the fact that the data is ready. As for this kind of signaling systemAsynchronismSo it is,PCI does not exist.
It interrupts VME and also the bus exists, corresponds to the interruption of 7 types of 68000. When the interruption occurs, it informs it has been about it will interrupt arrange module and it will output level to address and to process the interruption of some level about. You must note, those are not to be the method of informing about card number this time. In other words in many cases the plural cards to interrupt, because level is shared, (the translation and annotation: When the peripheral device card of the same type is a plural and the like). As for abundance of interruption level there is many a thing which is pointed out that it is the going too far of the design of 68000. Furthermore when it applies that to the bus, meaning is not formed.
As for the transfer with VME everythingDMA, each card becomes master and the slave. Concept of this is various with bus standard. For example,ISA busでは、既存の「チャネル」モデルを使っている。すなわちホストCPUが全ての通信を制御する方式である(チャネル・コントローラ参照)。 その点、VMEはコンセプトとしては非常に単純であるが、そのために各カード上に複雑なコントローラを必要とする。
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