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I know my computer upgrade will not have ISA slots. What other measurement products are available?

Question :

I know my computer upgrade will not have ISA slots. What other measurement products are available?

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Product(s) :
PCI/ISA Plug-In Boards: various


Question : I know my computer upgrade will not have any ISA slots. What alternate measurement products can I use?

Answer: Today, most new PCs contain few if any ISA slots unless you are purchasing from an industrial computer vendor. However, a tremendous number of ISA data acquisition boards were designed into production and R&D systems over the last five to ten years. Unfortunately, those needing to replace boards or duplicate whole systems usually find that PCI drop-in equivalents are rare. This requires considering hardware and software compatibility issues to make the switch to PCI.

When migrating from ISA boards, the most obvious task is to find a PCI board with capabilities similar to the ISA board you're trying to replace. However, this should not be done purely on product specifications, but rather on the requirements of the application. For example, the ISA board may have 32 lines of digital I/O by the data sheet, but if you use only a portion of them, a PCI board with fewer could be sufficient. Additionally, with the advent of surface mount technologies used on PCI cards, it is not uncommon to be able to replace multiple ISA boards with a single PCI board due to more features available from a single card: AI, AO, DIO and CT.

Speed and feature density of benchtop instruments are also increasing, so the ideal upgrade from an ISA board may not be a PCI board at all, but maybe an ethernet based product such as the Model 2701. The 2701 can perform single channel sampling as fast as 3500/sec into an internal memory buffer large enough for 450,000 samples. The 2701 can read and transfer data over ethernet at rates up to 1600/sec. When used with switching modules in it's two available slots, the 2701 becomes a multi-channel measurement and control system. From a software standpoint, the 27xx mainframes of the Integra Series can be computer controlled via their bus interfaces (RS-232, GPIB or Ethernet) with simple string commands. So in addition to the Windows based IVI drivers and start up software, control from DOS or Linux based systems is also quite easy.

In many cases, it might not be possible to find a board with the same channel counts, I/O connector, and pinout specifications. This connectivity problem can require a rewiring job and redesign of signal conditioning--a potentially expensive, time-consuming task, especially for multiple systems running on a production line. Keithley does offer some ease of connection upgrades:

ISA Boards
PCI Board(s)
Screw Terminal Adaptor Required

PIO-12, PIO-24



PIO-96, PIO-96J



PIO-96, PIO-96J






In terms of software, most ISA boards are I/O mapped, while most PCI boards are memory-mapped. This creates a difference in addressing schemes that can require rewriting software, depending on which driver architecture your software uses.

If your ISA board is programmed using Port I/O ('register-level programming'), the program must be rewritten for the memory mapped PCI board. Your programming language needs to be able to access the 32bit registers of the card. Furthermore, PCI boards are Plug-and-Play devices so do not have base address switches to control what addresses they inhabit; your program needs to be able to enumerate the PCI bus to detect the card and to read out the assigned configuration.

Register level control of PCI cards requires a significantly different skill and tool set than was required for ISA boards and often is done with third party tools like WinRT to gain real mode access into 32bit memory space.

For software using a Windows device driver model, the migration can be much easier, especially if the data acquisition vendor provides a hardware independent driver set, such as Keithley's DriverLINX device driver. If an ISA board is programmed with it's DriverLINX driver, then migration to a PCI board can be quite simple requiring as little as just one line of code to be changed. If your software is used under DOS and you're trying to migrate to Windows, it will have to be redesigned, regardless of the ISA/PCI differences.

In all cases, the migration from ISA boards will require some work. Careful consideration of what the application requires and making realistic assumptions about the amount of time required will ease the over all stress of the journey.

©Copyright 2003, Keithley Instruments, Inc.

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