ADLINK cPCI-3720: 3U CompactPCI Low Power Pentium III CPU Module

ADLINK cPCI-3720: Technical Analysis of 3U CompactPCI Low Power CPU Module Based on Mobile Pentium III

In the fields of industrial control, telecommunications infrastructure, military electronics, and transportation, the CompactPCI (cPCI) bus platform has long been an ideal choice for building critical mission systems due to its robust Eurocard mechanical structure, excellent heat dissipation performance, highly reliable connector design, and redundant power support on the backplane. With increasingly stringent requirements for power consumption, heat dissipation, and spatial layout in the system, the 3U CompactPCI (100mm × 160mm) specification occupies an important position in many applications due to its compact size and flexible configuration.

The ADLINK cPCI-3720 series 3U CompactPCI low-power CPU module is designed specifically for this type of application. It is based on the Mobile Intel Pentium III processor and Intel 440MX chipset, achieving complete x86 PC functionality in a compact 3U space while controlling power consumption at an extremely low level. Its flexible slot configuration (1 slot/2 slots/3 slots), dual 10/100Mbps Ethernet, configurable serial port, and hot swappable support make it an ideal choice for embedded applications with strict requirements for power consumption, heat dissipation, and reliability, such as telecommunications access equipment, railway signal control, and military data acquisition systems.

Overview of Product Positioning and Hardware Architecture

The cPCI-3720 series is a 3U CPU module that fully complies with the PICMG 2.0 Rev. 3.0 CompactPCI specification, with dimensions of 100mm × 160mm. It is designed as the system slot main control CPU, but also supports running in peripheral slots (without occupying CompactPCI bus communication). This series offers multiple model variants to meet the performance, storage, and space requirements of different application scenarios:

Model Slot Width Processor Built in Storage Applicable Scenarios

CPCI-3720A/P72 1 slot (4HP) Pentium III 700MHz CompactFlash (via mezzanine card) ultra compact, low-power, no mechanical hard drive application

CPCI-3720A/C42 1 slot (4HP) Celeron 400MHz CompactFlash (via mezzanine card) cost sensitive, low-power applications

CPCI-3720B/P72 2-slot (8HP) Pentium III 700MHz 2.5 "ATA HDD+CompactFlash for mainstream applications requiring large capacity local storage

CPCI-3720B/C42 2 2 Slot (8HP) Celeron 400MHz 2.5 "ATA HDD+CompactFlash Cost Sensitive+Local Storage Requirements

In addition, with additional mezzanine card support, it can be expanded to a width of 3 slots (12HP) to accommodate devices such as ultra-thin floppy drives (FDD).

1. Processor and chipset: the essence of low-power mobile platforms

The cPCI-3720 series uses Intel Mobile Pentium III BGA2 processor (0.18-micron process) or Mobile Celeron processor, which is a low-power version designed specifically for mobile computing and runs at a much lower voltage than desktop processors. Main parameters:

Pentium III 700MHz: 100MHz FSB, 256KB on-chip full speed L2 cache, suitable for applications that require higher integer and floating-point performance.

Celeron 400MHz: 100MHz FSB, 128KB on-chip full speed L2 cache, cost-effective option.

Chipset: Intel 440MX, which is a highly integrated chipset designed by Intel for mobile and embedded platforms. It integrates northbridge and southbridge functions into a single chip, significantly reducing power consumption and PCB area.

2. Memory support

Equipped with a 144 pin SO-DIMM slot, supporting PC-100 SDRAM with a maximum capacity of 256MB. The memory type must be 3.3V SDRAM. This capacity is sufficient to meet the majority of task requirements for running lightweight embedded operating systems (such as Windows NT/2000, VxWorks, QNX, embedded Linux) and control applications. ADLINK provides OEM bulk pre installed memory services.

Deep analysis of key characteristics

1. Flexible network configuration: Dual Intel 82559 Ethernet controllers

CPCI-3720 provides two Intel 82559 Fast Ethernet Multifunction PCI Controller 10/100BaseTx Ethernet channels. 82559 integrates MAC and PHY into a single chip, making it a mature, reliable, and widely driven industrial grade Ethernet controller.

LAN1: Only supports front panel I/O (RJ-45 interface).

LAN2: Supports front and back panel I/O (via cPCI-R3720 RTM), and selects whether LAN2 signals are routed to the front or back panel through onboard DIP switches (S2 and S3). The front and rear panels cannot use LAN2 simultaneously.

The dual port design supports network redundancy (such as link aggregation) or physical isolation between the management network and the data network, making it suitable for application scenarios that require high reliability communication (such as telecommunications billing systems, remote monitoring gateways).

2. Rich serial interfaces and configurability

CPCI-3720 provides two 16C550 UART compatible serial ports:

COM1: Only lead out to the DB-9 interface through the J2 rear wiring connector (cPCI-R3720). Through the jumper wires (JP1-JP4) on cPCI-R3720, COM1 can be configured as:

RS-232 (default)

RS-422 (differential signal, long-distance point-to-point communication)

RS-485 (Multipoint Bus, Half Duplex)

RS-485+(Enhanced RS-485 with Automatic Direction Control)

COM2: Supports both front panel RJ-45 interface and J2 rear wiring, but cannot be used simultaneously. COM2 is the standard RS-232 interface.

Both serial ports support complete hardware flow control signals and a transmission rate of up to 115.2K Baud. Of particular note is that the RS-485+mode of COM1 integrates automatic direction control function. When performing RS-485 half duplex communication in a Windows environment, the hardware automatically manages data direction switching without software intervention, effectively avoiding communication conflicts caused by software timing issues.

3. Flexible storage solutions

CPCI-3720 offers multiple storage options to meet different application needs:

2.5-inch ATA HDD (B-series 2-slot version only): Install a 2.5-inch ATA hard drive with a thickness not exceeding 9.5mm through a dedicated HDD mezzanine mechanism. ADLINK provides an HDD accessory kit (P/N: 58-00023-000), including a 44 wire IDE connector and screw kit. This design provides convenience for applications that require large capacity local storage, such as data logging and log storage.

CompactFlash (all models): CF Type II slots are provided through the CompactFlash mezzanine card, supporting CF storage cards ranging from 8MB to 512MB. CF cards are very suitable for installing embedded operating systems and core applications due to their anti vibration and wide temperature working characteristics.

Flash2000 flash drive: Supports Flash2000 flash drives (32MB to 512MB) based on 2.5-inch IDE interface, providing reliability for solid-state storage.

4. IEEE-1284 parallel port and USB interface

Parallel port: It is wired out through J2 and supports SPP/ECP/EPP mode, complying with the complete IEEE-1284 specification. The default configuration is LPT1 (ISA I/O address 378h, IRQ7).

USB interface: Supports two USB 1.1 ports. USB-A is located on the front panel (Type A connector), and USB-B is led out through J2 wiring. Each port provides standard 500mA overcurrent protection.

5. PS/2 keyboard and mouse interface

The front panel provides a 6-pin circular DIN connector (PS/2), which can be connected to both the PS/2 keyboard (purple) and mouse (green) through the Y-shaped distribution cable provided by ADLINK. If Y-cable is not used, only keyboard connection is supported.

6. Front panel LED indicator light and reset button

Green Active LED: System operation indicator.

Red HDD LED: IDE/ATA bus activity indicator.

Amber WDT LED: Watchdog timer timeout alarm indication.

Blue General Purpose LED: for users to customize.

Embedded reset button: supports system hardware reset.

Deep Analysis of Watchdog Timer

In industrial embedded systems, watchdog timers are one of the key technologies for achieving high system availability. CPCI-3720 has implemented a powerful watchdog timer through the logic device 8 of Winbond W83977EF Super I/O chip.

1. Working principle

WDT is essentially a hardware down counter. The application starts counting after setting the initial value. Under normal operation, the application needs to periodically 'Reload' the dog before the counter resets to zero. If the system deadlocks and the dog is not fed in a timely manner, the WDT will send a reset signal (RESET) or NMI interrupt (configurable through BIOS) to the system after the counter is reset, forcing the system to recover.

2. Configurable timeout range

Second level resolution: timeout range 1 to 255 seconds, with a step of 1 second.

Hierarchical resolution: timeout range 1 to 255 minutes, step 1 minute.

3. Keyboard/mouse wake-up reload

When Bit 2 and Bit 1 of the CRF3 register are set, any keyboard key or mouse movement event will trigger the reload of WDT. This design is very practical in systems with human-computer interaction interfaces - as long as the operator is still operating the terminal, the system will not reset due to watchdog timeout.

4. Programming points

The configuration of the watchdog timer should follow the standard LPC configuration process:

Write 87h twice to I/O port 3F0h to enter extended function mode.

Configure the relevant registers (CRF2, CRF3, CRF4) of logic device 8 to set timeout values, enable WDT, and configure interrupt response.

Write 0Ah to I/O port 3F0h and exit the extended function mode.

ADLINK provides sample programs and subroutine libraries for DOS, Windows 95/98/NT/2000, simplifying integration work.

Rear Routing Module (RTM) - cPCI-R3720

CPCI-R3720 is a standard 3U CompactPCI rear wiring transition module (RTM, 4HP width) designed specifically for cPCI-3720. It routes onboard signals to the back of the chassis through J2 connectors, facilitating cable management and maintenance. Its main functions include:

Interface Type Description

COM1 DB-9 (panel) RS-232/422/485/485+configurable (via jumper)

COM2 10 pin onboard pin RS-232 standard

LAN2 RJ-45 (panel) 10/100Base-T Ethernet

USB-B Type B (Panel) USB 1.1

LPT 26 pin onboard pin parallel port

PS/2 KB/MS panel keyboard mouse combination interface

Important note: COM2, keyboard, mouse, and LAN2 support both front and back panel I/O, but the front and back panels cannot be connected to devices simultaneously. Simultaneous connection may cause damage to I/O ports or system modules, and void the warranty.

Compatibility between software and operating system

1. Operating system support

CPCI-3720 is compatible with all mainstream PC operating systems, including:

Windows 95/98、Windows NT 4.0、Windows 2000。

VxWorks (a real-time operating system widely used in the telecommunications and military industries).

Linux (supported by the community).

2. BIOS

Adopting Award PnP BIOS, based on 2Mb (256KB) Flash ROM, supporting:

DMI (Desktop Management Interface): allows users to query hardware level information such as CPU type, frequency, and memory size.

PXE (Preboot Execution Environment): Supports remote system boot or installation of operating systems over a network.

Remote console support: Remote BIOS configuration and system management through serial port.

BIOS write protection: Provides antivirus capabilities.

Power Management and Thermal Design

1. Low power design

The low-power characteristics of the Mobile Intel Pentium III processor and 440MX chipset are one of the core advantages of cPCI-3720. The measured power consumption data is as follows:

Load condition 3.3V current 5V current Total power consumption

Idle load 0.919A 1.268A~8.46W

Average load 1.465A 2.587A~16.85W

Full load (100% CPU+HCT test) 2.488A 2.801A~21.27W

Such low power consumption allows cPCI-3720 to operate stably in a 3U chassis with almost no need for special heat dissipation design, even in a sealed chassis. This greatly simplifies system design and improves reliability.

2. Hot swappable support (PICMG 2.1)

The hardware design of cPCI-3720 fully complies with PICMG 2.1 CompactPCI hot swappable specification Rev. 2.0:

Power ramp circuit: controls the orderly rise of voltage and eliminates high voltage or current spikes during hot swapping.

Hot swappable operation: In a single SBC operating environment (without peripherals), users can remove or insert cards without the system being powered on. Pull the pop-up lever to trigger the power shutdown sequence, the green power LED will turn off, and the blue hot swappable LED will light up to safely remove it. After successful insertion, the blue LED will turn off and the green LED will light up.

Caution: If the hot plug function is not required, it is recommended to disable it in the BIOS to free up interrupt resources.

3. Hardware Doctor

Through the Winbond W83L784R hardware monitoring chip, cPCI-3720 supports:

CPU temperature monitoring

System temperature monitoring

System voltage monitoring (3.3V, 5V, 12V, etc.)

CPU fan speed monitoring

ADLINK provides the Hardware Doctor Utility (supporting Windows 98/NT), which pops up a warning to remind users to take appropriate measures when any monitoring parameters exceed the normal range. This is particularly important for unmanned equipment.

Best Practices for Application Scenarios

Scenario 1: Telecommunications access equipment (SS7 signaling gateway)

The SS7 signaling gateway of a telecommunications equipment manufacturer uses cPCI-3720B/P72 as the main control CPU module. The processing power of Pentium III 700MHz is sufficient to run signaling protocol stack and routing management software; Dual Ethernet ports are connected to the signaling network and management network respectively, achieving physical isolation; CompactFlash stores embedded Linux operating systems and configuration files to ensure quick system recovery after power failure; Hot swappable support allows for on-site maintenance without interrupting the entire machine service; Low power design (<17W average power consumption) reduces the noise of chassis cooling fans and is suitable for deployment in operator data centers.

Scenario 2: ATP onboard system for rail transit

The automatic protection (ATP) system of a certain train needs to integrate CPU, digital I/O, and communication modules in a 3U cPCI chassis. The low power consumption characteristic (<10W) of cPCI-3720A/C42 (1 slot, Celeron 400MHz) allows it to operate in a closed car chassis without the need for an active fan. COM1 is configured to communicate with remote diagnostic terminals in RS-422 mode, while COM2 is connected to the train bus gateway. 2.5-inch HDD records operation logs and CF card stores system firmware. The hardware monitoring function tracks the CPU temperature in real-time to ensure the reliability of train operation during high temperature seasons.

Scenario 3: Military Industry Data Collection and Processing System

The data acquisition system of a certain national defense project needs to operate in a multi vibration, wide temperature environment, and has strict limitations on power consumption. CPCI-3720A/C42, combined with CompactFlash solid-state storage, has no mechanical moving parts and excellent vibration resistance. Its industrial grade operating temperature range and low-power design meet military standards. The GPIO (GPO1-4, via slot DB-9) of Winbond W83977EF can be directly connected to external status sensors without the need for additional I/O cards.

Scenario 4: Upgrading and Replacing Old Systems

The CNC control system of a certain factory is still using industrial control computers based on ISA/PCI full-length cards, facing problems of motherboard aging and difficult maintenance. By using cPCI-372B/P72 in combination with cPCI-R3720 RTM, the original 3U cPCI chassis and backplane can be used, while retaining high-value dedicated ISA/PCI expansion cards (connected through the backplane). The software is based on Windows NT 4.0 and can be directly migrated (ADLINK provides complete driver support). This solution extends the service life of the equipment without the need for large-scale rewriting of control software.

Key points of engineering deployment

1. Memory selection and installation

Only supports PC-100 144 pin SO-DIMM 3.3V SDRAM.

Suggest using ADLINK certified memory modules. Ensure that the module is securely inserted during installation and does not exceed the height limit, otherwise components may be damaged when inserted into the chassis.

2. LAN2 front panel/rear panel selection

Set through onboard DIP switches S2 and S3:

Front panel LAN2: S2 all ON, S3 all OFF.

Rear panel LAN2: All S2 are turned off and all S3 are turned on.

Do not connect LAN2 on both the front and back panels at the same time, as this may cause network conflicts or hardware damage.

3. COM1 mode configuration (cPCI-R3720)

Select through JP1-JP4 jumper:

RS-232 (default): JP1-JP4 are all Unused.

RS-422/485/485+: Please refer to the user manual table for configuration.

In RS-485 mode, if using RS-485+mode, the corresponding jumper combination needs to be selected to enable automatic direction control.

4. Installation of 2.5-inch HDD (B series)

Only supports low profile ATA HDDs with a thickness not exceeding 9.5mm.

Use the 4 copper pillars and 44 wire IDE connector from the HDD accessory kit (P/N: 58-00023-000).

During installation, pay attention to aligning the PIN1 of the IDE connection cable and ensure that all screws and connectors are securely fixed.

5. Suggestions for the installation sequence of drivers

For Windows NT systems, it is recommended to install LAN drivers first and then install service packs.

If there is a system startup warning or exception, it is recommended to reinstall the Windows NT Service Pack and install the drivers in a different order.

Tips for troubleshooting common engineering problems

Problem phenomenon 1: The system cannot be powered on or the power LED does not light up

Key points of inspection: Confirm that cPCI-3720 is fully inserted into the chassis backplane and lock the ejection device. Check if the backplane power supply is normal (3.3V, 5V, and 12V).

Key point: The power ramp circuit of cPCI-3720 requires unconditional reset when the voltage is below 3.0V (3.3V), 4.75V (5V), and 10.0V (+12V). If the power quality is poor, it may lead to frequent resets.

Problem phenomenon 2: LAN2 cannot communicate

Key points for inspection: Confirm that DIP switches S2/S3 are set correctly (front or rear panel). Confirm if LAN2 is connected to both the front and rear panels simultaneously.

Key point: The front and rear selection of LAN2 is only controlled by hardware DIP switches and does not involve BIOS settings. If the switch is set incorrectly, the operating system cannot recognize the network port.

Problem phenomenon 3: Communication abnormality of COM1 in RS-485 mode

Key points of inspection: Confirm that the JP1-JP4 jumper settings on cPCI-R3720 match the selected RS-485 mode. Check the terminal resistance configuration of external devices.

Key point: If using RS-485+mode, confirm that the jumper configuration is the corresponding automatic direction control combination. Incorrect jumper settings will result in data direction switching failure.

Problem phenomenon 4: The system frequently resets automatically

Key inspection points: Use the Hardware Doctor Utility to check if the CPU temperature and system voltage are normal. Confirm if the watchdog timer has been accidentally enabled and correctly fed to the dog in the application.

Key point: Temporarily disable the watchdog function in BIOS for troubleshooting testing. If the reset disappears, the problem lies in the WDT configuration or the dog feeding logic of the application.