At present, the application of embedded computer systems presents a trend of diversification, miniaturization, and multi-level, and plays an increasingly important role in industrial field and military applications. With the increasing requirements of various applications on operating systems and software, embedded computer systems with a wide range of adaptable PC architectures are becoming more and more popular. In particular, the widespread application of the Compact PCI bus in industrial and military fields provides more application environments for PC-based embedded computer systems. However, for a computer system, the development cycle of the host is generally longer and more complex. Compulab developed a series of embedded PC modules to provide new ideas for the development of PC-based embedded computer systems. In other words, the embedded PC is used as the core, and an embedded computer adapted to various bus requirements is developed through various bus bridge circuits. At the same time, it also provides an effective way for rapidly improving the performance of various embedded computer systems. This article describes a design example of an embedded computer system with Compulab's family of embedded PC modules as its core.
1. Compulab 786CoreThe 786Core produced by Israel's Compulab is a small, powerful and cost-effective single-board embedded PC module.
It applies to all kinds of embedded applications based on PC architecture. The 786Core is equipped with various chipsets required for operating systems such as Windows, Linux, VxWorks and DOS, and is equipped with a corresponding BIOS. Embedded PC module 786Core has the characteristics of small size and strong functions. The entire module area is only 99mm & TImes; 69mm, but integrated PenTIumIII/Celeron400 ~ 700MHz CPU, 32 ~ 256M SDRAM, LPC, 5V compatible PCI and AC97 bus control, also provides VGA/SXGA, two USB interfaces, two PS / 2 interfaces, two 10Mbps/100Mbps Ethernet interfaces, ATA IDE interface, floppy drive interface, one RS 232 and one RS 422 serial port. In order to adapt to embedded applications, 786Core also has embedded BIOS. 786Core's architecture diagram see
The powerful and flexible features of the 786Core provide a broader design space for embedded computer system designers. In particular, the Compact PCI bus architecture developed through the PCI bus has expanded the functionality and application of the embedded system. However, due to the special nature of the electrical performance and protocol of the Compact PCI bus, the difficulty of the device development based on this bus can be imagined. A variety of PCI bridge logics are commonly used to convert the operations on the Compact PCI bus into other, simpler bus operations.
2.Based on the 786Core embedded computer system design and implementation of the emergence and development of embedded PC modules, and the extensive application of various bridge circuits based on the PCI bus, the development cycle of the embedded computer system is greatly shortened, and directly improve the practicality of the system. Sexual and software application flexibility.
2.1 System Organization and Structure Figure 2 depicts a high-performance embedded computer system with a PIII CPU as its core. It includes 16 differential input A/Ds, 4 RS-232/422 serial ports, and dual 8139 Ethernet controllers, as well as a chassis-corresponding harsh environment power supply. All modules of the system are standard 3U size, and the chassis is a reinforced 4-slot 3U chassis. Because the PCI bus provided by the embedded PC module can not provide enough load capacity, the host module must add a PCI-PCI bridge chip - Intel S21152BB. The PCI bus provided by this chip can support four PCI devices. The devices on the bus must and only be the only load for the Compact PCI bus. If you want to increase the load, you must have a load capacity that bridges the chip expansion bus. Double network module in Figure 2. Since the two Ethernet controllers RTL8139D in the module are the PCI bus loads, the bus is first expanded through the PCI-PCI bridge chip - Intel S21152BB, and the functions of the two Ethernet cards are completed. In addition, as a Compact PCI bus system, all modules, including the backplane, are designed according to the PCI PCI 2.0 R2.1 Compact PCI specification, including the termination resistor design (Figure 2), backplane clock and interrupt design, and other electrical performance. the design of.
2.2 Design and Implementation of Expansion Modules In this system, there are three expansion modules in addition to the host module. They complete the system's sampling and processing of analog signals (AD module), communication between the system and other devices (4 serial-port modules) and the system. Connection to the Internet (dual network module). In addition to the PCI-PCI bridge chip that is required for the dual network module mentioned above in this system, the connection between the AD module and the serial module and the CPCI bus also requires the support of the bridge chip AMCC S5920 (as shown in Figure 2). The AMCC S5920 is a single-chip, multi-function device that offers designers a flexible and easy path to the PCI bus. By using the S5920, the module designer does not need to consider the special requirements of the various electrical properties and timing of the PCI bus. It is only necessary to design according to the ADD-ON bus of the ISA-like TTL level converted by the S5920. As the target device on PCI, S5920 can provide 132Mbps data transfer rate, compatible with 33MHx PCI bus and ADD-ON bus up to 40MHz, the ADD-ON bus converted by it can support 8, 16 and 32-bit data width .
(1) The AD module supports 16 analog differential inputs. The signal sampling and AD conversion are performed by the AD976. The sampling result is smoothed by the single-chip microcomputer 89C52 and sent to the CPLD through the optoelectronic isolation device. The CPLD is then stored in the static RAM for the upper computer to read. take. The module occupies 32 bytes of 8-bit wide I/O space and is used to store 16 channels of 16-bit precision AD sampling results. (2) The serial port module supports 4 RS-232/422 serial ports through the CD1865, occupying 512 bytes of 8-bit wide I/O space and 1 interrupt.
2.3 Software Design This system uses VxWorks embedded operating system. It is one of the most unique operating systems in all current processor-independent real-time systems. VxWorks micro-kernel Wind is a high-performance, standard embedded real-time operating system kernel. Its main features include: rapid multi-task switching, preemptive task scheduling, and diversification of communication methods between tasks. The kernel has the characteristics of short task switching time, small interrupt latency, large network traffic, etc. Compared with other embedded real-time operating systems, it has certain advantages. Drivers for all modules are developed under VxWorks and the development environment is Tornado II. It is the latest generation of development and debugging environment in the embedded real-time field, and it is a complete software development platform for realizing embedded real-time applications. Drivers for each module of this system are written in C language and compiled under Tornado II. O files are provided to users as secondary development middleware. The operating system and application programs are stored on the 192MB electronic disk of the host module, which greatly improves the running speed of the software and allows the system to work in environments where the temperature and stability conditions are very harsh.
2.4 Features and Technical Specifications of the System
(1) High-performance PIII 700MHz CPU core, 128M SDRAM, 192MB electronic disk;
(2) Support multiple operating systems: DOS, VxWorks, Windows XP/2000, Linux, etc.
(3) Serial module: 4 full-duplex asynchronous serial ports, transmission rate up to 115.2kbps, different serial communication modes can be selected through software settings, RS-232 (V.28) or RS-422 (V.11, X .twenty one)
(4) AD module: 16 analog differential inputs, support AD data intelligent conditioning, AD conversion time up to 5μs/Sample, effective input signal range: -15V～+15V, analog sampling part and CPCI bus digital part photoelectric isolation
(5) Dual network card: 10Mbps/100Mbps autosensing Ethernet to support automatic fault diagnosis, switching and recovery;
(6) Innate reinforcement seismic design;
(7) thermal conduction heat dissipation design;
(8) Electromagnetic Compatibility Design;
(9) 3U standard size.
The embedded computer system described in this paper has a wide range of applicability. Due to its inherent reinforcement, seismic and heat transfer design, it is highly adaptable in particularly harsh industrial and military environments. In addition, the design process of the system is an effective way to rapidly develop embedded computer systems, and it is easier to form a series of products to improve the market competitiveness of products.
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