The CC770 CAN Controller

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The CC770 CAN controller from Bosch can directly replace Intel’s AN82527 for spare parts and further development.

In the CC770 CAN controller, Bosch is adding a substitute for Intel’s AN82527 CAN controller to the company’s range. The device has a high level of structural equivalence to the Intel chip.

Intel is no longer accepting orders for the AN82527, and will cease production by the end of 2007. The CC770 will remain available to cover the need for spare parts and for the purposes of further development.

CAN (Controller Area Network) controllers in vehicles control the flow of data between electronic control units over the serial CAN bus. They are fitted to a very large number of vehicles, and must, as an automobile specific spare part, remain available over a long period.

The CC770 is compatible in both pins and functions with the overwhelming majority of all AN82527 applications. No other CAN controller offers such high compatibility with the AN82527 as the Bosch IC. Both integrated circuits are available in PLCC44 packages. Intel permits surface mounting (SMD) in the QFP44 housing, while Bosch offers the lower profile LQFP44 housing.

The most important condition for direct exchange is that the AN82527 must access the CAN bus through an external bus driver in the application concerned. This is true for the majority of applications. Only a few early circuits designed with the AN82527 use the controller’s internal bus driver, as external drivers were not available at that early time. Direct exchange is not possible in such applications.

Having been developed significantly later, the CC770 incorporates a number of structural improvements over the Intel controller, and these can be helpful in further development projects. It is, for instance, no longer necessary to fear data corruption during fast reads. The new “silent” mode is also advantageous. This allows developers, typically when fault finding, to observe the CAN bus traffic without having to add an extra bus node just for this purpose.

 

FEATURES With the CC770, Bosch is offering a high level of equivalence to the AN82527 Direct exchange possible - compatible in both pins and functions

 

What is CAN?
CAN is a serial bus system especially suited for networking "intelligent" devices as well as sensors and actuators within a system or sub-system.

 

The Attributes of CAN
CAN is a serial bus system with multi-master capabilities, that is, all CAN nodes are able to transmit data and several CAN nodes can request the bus simultaneously. The serial bus system with real time capabilities is the subject of the ISO 11898 international standard and covers the lowest two layers of the ISO/OSI reference model. In CAN networks, there is no addressing of subscribers or stations in the conventional sense, but instead, prioritized messages are transmitted. A transmitter sends a message to all CAN nodes (broadcasting). Each node decides on the basis of the identifier received whether it should process the message or not. The identifier also determines the priority that the message enjoys in competition for bus access. The relative simplicity of the CAN protocol means that very little cost and effort need to be expended on personal training; the CAN chips interfaces make applications programming relatively simple. Introductory courses, function libraries, starter kits, host interfaces, I/O modules and tools are available from a variety of vendors permitting low cost implementation of CAN networks. Low cost controller chips implementing the CAN data link layer protocol in silicon and permitting simple connection to microcontrollers have been available since 1989. Today there are more than about 50 CAN protocol controller chips from more than 15 manufacturers announced, and available.

The use of CAN in most of European passenger cars and the decision by truck and off-road vehicle manufacturers for CAN led to the availability of CAN chips for more than 10 years. Other high volume markets, like domestic appliances and industrial control, also increase the CAN sales figures and guarantee the availability for the future. Up to spring 1997 there have been more than 50 million CAN nodes installed. One of the outstanding features of the CAN protocol is its high transmission reliability. The CAN controller registers a stations error and evaluates it statistically in order to take appropriate measures. These may extend to disconnecting the CAN node producing the errors.

Each CAN message can transmit from 0 to 8 bytes of user information. Of course, you can transmit longer data information by using segmentation. The maximum transmission rate is specified as 1 Mbit/s. This value applies to networks up to 40m. For longer distances the data rate must be reduced: for distances up to 500m a speed of 125 kbit/s is possible and for transmissions up to 1km a data rate of 50 kbit/s is permitted.

 

 

CAN Applications
CAN networks can be used as an embedded communication system for microcontrollers as well as an open communication system for intelligent devices. The CAN serial bus system, originally developed for use in automobiles, is increasingly being used in industrial field bus systems, the similarities are remarkable. In both cases some of the major requirements are: low cost, the ability to function in a difficult electrical environment, a high degree of real time capability and ease of use.

 

 

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