• Unique DMA Technique Supports High-Speed Transfers of Analog, Digital, and Counter Data Simultaneously
• Pre-Trigger and Post-Trigger Capture of Event Data
• DMA, Interrupt-Driven, or Polled Modes of Operation
• Inter-Board Bus Allows Data Transfers Between Boards
• Functionality Determined by up to Three Plug-In I/O Modules

The PCI-20041C-2A and PCI-20041C-3A (DMA version) are customizable data acquisition boards that interface directly with the internal bus of ISA (PC/XT/AT) computers. The boards have 32 points of fully buffered digital I/O already on board, and you can expand their I/O capabilities by adding up to three plug-in option modules. The option modules provide analog input, analog output, digital I/O, counter/timer, quadrature decoder, simultaneous sample/hold, and analog triggering/alarm functions.

The PCI-20041C Series boards provide the mounting space, power, and inter-module communications required to support three option modules. Digital, sync, and analog signals pass between modules via the on-board Intelligent Instrumentation Interface (I3) Bus. An inter-board communications port permits similar communications between boards so that you can employ up to 15 option modules. Thus, configurations can range from relatively simple systems with a small number of I/O points to sophisticated systems with several hundred I/O channels and high-speed capability. All power is derived from the +5V DC power supply of the PC. A DC/DC converter on the each board generates regulated ±15V DC power for use by the modules. When you use option modules with a PCI-20041C Series board, the connecting cables should be routed through the unused PC expansion slot opening. A PCI-20028A-3 strain-relief bracket is available to support the I/O cables.

On-Board Digital I/O
Both the PCI-20041C-2A and PCI-20041C-3A boards have 32 points of fully buffered digital I/O. The 32 points are arranged in four groups (bytes) of eight bits. You can configure each byte for either input or output use via software. You can expand the number of on-board digital channels to 128 using PCI-20004M-1 option modules.

Pacer Clock
Both boards have an 8MHz programmable pacer clock for timing data acquisition and transfers of data to and from memory. Both the PCI-20041C-2A and the PCI-20041C-3A can operate in the programmed transfer mode using either polling or interrupt techniques. Each board supports a single interrupt to the host computer. The interrupt can be jumpered to levels 2 through 7.

DMA Support
A unique, patented DMA technique gives the PCI-20041C-3A board the ability to make very high-speed transfers (up to 360K bytes/sec) of input (or output) data to (or from) the memory of the PC. The DMA controller in the host computer is used in conjunction with a controller on the board to accomplish the transfer invisibly to the host computer. Data is transferred to or from the memory of the host PC in frames of up to 64K bytes. You can initiate DMA transfers on command or on the occurrence of an event after delay. Similarly, you can terminate transfers on command, on the occurrence of an event after delay, or after transferring a specified number of frames of data. Transfers can be timed by the on-board pacer clock or by the occurrence of events. Transfers of data to a circular buffer can be used to give pre- and post-trigger information. This allows the analysis of conditions both before and after the occurrence of a random critical event.

Inter-Board Bus
The inter-board communications port allows a designated PCI-20041C Series board to operate as a master and to control DMA transfers from up to four other boards, which operate as slaves. By chaining boards together in this way, it is possible to make DMA transfers to or from up to 15 modules residing on the boards.

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