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

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