This section provides overview, applications, and principles of vme interface boards. Also, please take a look at the list of 5 vme interface board manufacturers and their company rankings.
VME (Versa Module Europe) boards were developed as boards that use the VME bus for CPUs.
The VME bus used in VME boards was originally developed for Motorola's 68000 series CPUs and was later adopted as a global technical standard by the IEC (International Electrotechnical Commission) and IEEE (Institute of Electrical and Electronics Engineers). It was later standardized as a technical standard by the IEC (International Electrotechnical Commission) and IEEE (Institute of Electrical and Electronics Engineers: a standardization organization in the electrical and information fields).
It is currently used as a standard bus for 64-bit CPUs in addition to 16-bit and 32-bit CPUs.
A VME board has 9 or 20 VME connectors on the motherboard, which is the foundation to connect multiple VME boards.
This motherboard is called a VME backplane board or VME backplane chassis, and its material and size are determined to maintain its performance and quality.
The VME backplane board is essential because it electrically and structurally connects multiple VME boards and transmits and receives data via this board.
The data transfer used by VME boards is based on the asynchronous interlocking method. This is different from the method of sending and receiving data synchronized with the system clock.
The master side repeats data transmission and does not complete the data transfer cycle until the slave side responds with an acknowledgment signal indicating that data reception is complete.
This is advantageous and easy to design for peripheral devices that do not have sufficient transfer speed since data can be sent and received according to the timing of the secondary device. However, it is necessary to avoid infinite transfer cycles from the master. For this purpose, the VME bus implements a timeout function.
Consideration is also given to the case of data collisions between devices on the VME bus. An arbitration module is a dedicated functional module for detecting and responding to collisions and must be present in every VME bus system.
Two methods are defined for detecting and responding to collisions. These are the round-robin method and the priority method.
Round-robin is a method in which each device on the VME bus is sequentially assigned a number based on the number assigned to the device. For example, if there are devices A, B, and C, and the first round is A, B, and C, the second round is B, C, and A, and the third round is C, A, and B. This method determines which device has priority when a collision occurs based on the rule that priority is switched equally in each round.
On the other hand, the priority method determines which device has priority in the event of a collision based on a fixed priority order for each device.
Which method is adopted should be determined according to the application and characteristics of the system.
*Including some distributors, etc.
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