Multiple networks

Multiple networks refer to those include the use of different communication media more than one of the network, the network group group within the existing home appliance devices integration control network manager, From each network group receiving the data transfer and send it to the network manager, will also from network manager receiving data into a suitable for each network group data and to transfer and thus in the use of different communication media network connection between realize communication group of communication media converter.

Multiple networks -- site equipment network

On site networking field has been found no is coherence or stability of the solution. When we just think field networks work may not stable, 2004 and 2005 based on Ethernet network happened incredible development.

Build multiple network equipment should be 2005 most actual equipment network schemes. System to ensure that legacy serial port and CAN provide the compatibility, and web based on CAN nets program web server interface. Based on browser installed, can find and solve problems and online documentation system itself can be solved. Specific methods are as follows:

A, multiple network hardware platform

To build multiple network, need many strategic equipment, including the daughter card, CAN external controller and gateways. A new type of feasible method is embedded in the selected Ethernet and thecan controller processing platform. These processors will serial ports, CAN of Ethernet and signals connected a signal packages that its price relative to offline Ethernet or thecan solution is more competitive.

From Freescale semiconductor freezing horses series 32 bit microprocessor is double network controller typical delegate. Many of them will Ethernet and thecan controller integrated into the same model, including some embedded with flash memory. Freescale MCF523x processor series is the next generation of ColdFire embedded memory typical.

Second, RTOS with TCP/IP protocol stack

Real-time operating system RTOS is complete control and distribution of CPU communications tasks of embedded system. In discussing RTOS before, it is necessary to explain many systems give up on the spot used in network RTOS for two reasons: high cost and product simple is they do not use RTOS reasons. But like the Freescale ColdFire products such a senior processor without RTOS is impossible, so in 2005 will seldom mention it costs - this is the main reason people give up it. In fact, love to use RTOS scheme of users understand the true price status, rather than RTOS will conceal its price. Method First, any Ethernet solutions are need TCP/IP protocol stack. Do not look down upon this free protocol stack, actually in and out of the time is always charge. When buying the TCP/IP protocol stack, you will find it costs may not little, even more, this is because RTOS actually contained in the TCP/IP protocol stack. Second, there was no RTOS system, designers often need to perform some internal schedule. No actual RTOS system is more complex, they used to replace the self-produced RTOS, which can cause huge the subsequent expenses. As time goes on, want to sell in the operating system add new features very difficult, this is because it cannot be easily changed properties caused. Results no RTOS scheme the cost more than product lifecycle.

Lack of complexity is not used RTOS another reason. In this paper, we discuss the consists of the Ethernet, CAN and one or more serial communication port multiple network system. By definition, owns the network interface system itself is complex, and the need for network interface RTOS the complexity and full service management. If the system can provide DeviceNet, Ethernet Modbus TCP/IP and communication of words, system is not possible simple.

Most strengthen control program (including most control component moving system) need to compute the three under the condition of the CPU resources allocation advanced control algorithm, low-level: control function and network connections. The advanced control algorithm is how calculation program to be controlled, these algorithms is very complex, requiring occupied large amounts of memory and CPU resources. Low-level control functions (e.g. timing function) seems to be very simple, but need long waiting times. In order to ensure service, lower control function is very likely to interfere with signal, but these by low-level control function caused by the interruption of interference will influence the advanced control algorithm of execution and performance.

ColdFire processor support will advanced control algorithm and low-level control function integrated unified block on new products. When ColdFire CPU execution RTOS and advanced control algorithm, will inaugarate eTPU coprocessor (called the embedded timing processing units) to handle all timed interference and complete the low-level control function. Low-level control function will not be subjected to convert impact, meanwhile the advanced control also won't be high-speed interference interrupts.

In contrast, most other processor not dealing with low latency, interference of resources, so must occupy CPU resource to meet real-time requirements. Coprocessor eTPU solved the core problem and make ColdFire CPU can concentrate on solving the advanced control code.

Three, choice of network application layer protocol

No matter whether you choose RTOS processor platform, multiple network system all need a set of network protocol. The software can handle bits of data and bytes of data transformation and through the network to send data to the corresponding program up. The network, it takes just a small set of application layer protocol. Overall has the following agreement.

Modbus (serial). Modbus is all network communication, and is the earliest standard list only of serial communication standards. Each device is by registers (16-bit unsigned integer) and coil (digits). The pact was set by the succinct information frame constitute a set of instructions. According to the capacity of the designer Modbus execution serial driver, so from these new legacy equipment to send or accepting the signal is still important.

DeviceNet (CAN). DeviceNet today is America's most important input/output (I/O) agreement, is based on CAN technology application layer protocol. CAN support single bus topological structure of buck. Although thecan CAN support thousands of nodes and make a data transmission rate reached 1-m potter, but DeviceNet will network knot points restricted to 64, baud rate control for 125K, 250K and 500K. On master-slave relations for linking DeviceNet based network, host station equipment from making a request to stand for the connection, control data and input/output data provide protocol connect. Once established input/output connections, standing by theory consulting, circulation or every change is submitted to communication mode and from standing connection.

CANopen (CAN). CANopen is another thecan application-layer protocol. Different is more connection guide, DeviceNet CANopen more information and guidance. CANopen support two kinds of basic information: service data information and processes data information. Service data information is large low priority information, and process data information is small higher-priority data. CANopen not based on connection, but support equivalence information of the agreement. In mass production mode, CANopen equipment is solely responsible for the production data, and don't care who to use it. CANopen by European widely accepted in the United States, in the approval of ascension.

EtherNet/IP. EtherNet/IP is applied to the control and ControlNet and DeviceNet information protocol (CIP) technical upgrade edition. Network each device is regarded as a series of object attribute values. EtherNet using TCP/IP (TCP) to convey information data, using UDP (non connecting equipment protocol) to deliver the input/output data. EtherNet/IP is Rockwell automation EtherNet and field device of communication standards.

Modbus/TCP. Modbus/TCP is applied on TCP/IP Modbus above. Modbus/TCP USES and has the same attributes and Modbus functions of registers (16-bit unsigned integer) and coil (bits). Besides Modbus/TCP information not contained cyclic redundancy check (CRC) outside, field Modbus and Modbus/TCP all information are the same. Because Modbus is very simple, it is field equipment system in widely realized.