DAS8JR BOARD DRIVER:

• Index
• Introduction - Supported Models and Features
• Configuration Parameters
• Board Menu Controls
• Connector Pinout Diagrams
• Revision History

INTRODUCTION:

                      MANUFACTURER'S SPECIFICATIONS:
                       ADC     Speed      DACs
                       Bits    µsec     # x Bits
  Computer
  Boards:
  CIO-DAS08/Jr          12     25         none
  CIO-DAS08/Jr-AO       12     25        2 x 12
  CIO-DAS08/Jr/16       16     30000      none
  CIO-DAS08/Jr/16-AO    16     30000     2 x 16

  CyberResearch:
  CYDAS 8JR             12     25         none
  CYDAS 8JRAO           12     25        2 x 12
  CYDAS 8JRHR           16     30000      none
  CYDAS 8JRAOHR         16     30000     2 x 16

None of these boards has a built-in pacer clock, so this driver uses the main system timer to control all sample timing.

DAS8JR CONFIGURATION PARAMETERS:

• Parameter Overview
• Address
• Bits Preset
• Channel Preset
• Help File Omit
• Model
• Parallel Port Address for Stimulus Output
  • Using an 8255 Port
  • Using an LPT Printer Port
• Conversion Speed
  • Special Notes for 16-bit Models

PARAMETER OVERVIEW:

    DAS8JR.ADC    A:h310 M:DAS08/Jr-AO

The parameter letters are case-insensitive, as are the entries that follow the colons.

Daqarta does not use any SET lines in your AUTOEXEC.BAT file, nor does it use any non-Daqarta drivers or libraries that may have been supplied by your board manufacturer.

You can check to see which parameters have been set, either via the configuration line or by default, by checking the board information summary available via the ALT-H Plug-In Help system. This also shows a summary of the default values for all parameters. There is no need to enter any parameter that is the same as the default value assumed by the driver.

A: ADDRESS:

    DAS8JR.ADC   A:h310

The value you enter is not validated against any standard list. Daqarta looks for the board at the address given, and if it does not find a valid DAS8JR compatible board there it exits with:

    'DAS8JR board not found.'

B: BITS PRESET:

This driver already supports four different 16-bit models, but note that the AO versions of these have 16-bit DACs to match. If a new model arises that has 16-bit ADCs but retains the 12-bit DACs, you could "fake" it by specifying one of the 12-bit AO models and also supplying the B:16 parameter, which only applies to the ADC.

C: CHANNEL PRESET:

    DAS8JR.ADC   C:3

F: HELP FILE OMIT:

Note that ALL Help files, including main, can be omitted via an F:0 parameter on the INIT line (first line) of the DQA.CFG file. If this is present, no individual module Help will be loaded.

M: MODEL NAME:

    DAS8JR.ADC   M:DAS08/Jr-AO

 'M: Model not recognized.  Supported models are:
  Computer Boards:
    DAS08/Jr
    DAS08/Jr-AO
    DAS08/Jr/16
    DAS08/Jr/16-AO
  CyberResearch:
    CYDAS-8JR
    CYDAS-8JRAO
    CYDAS-8JRHR
    CYDAS-8JRAOHR'

For boards from other makers you must use the closest equivalent model from the above list. Compare the features of your board with those in the features table to assist in this determination.

If you omit the M: parameter, a basic DAS08/Jr board will be assumed.

P: PARALLEL PORT ADDRESS FOR STIMULUS USE:

To specify the internal port, use:

    DAS8JR.ADC   P:I

USING AN 8255 PORT FOR DIGITAL STIMULUS OUTPUT:

An 8255-type port occupies 4 consecutive addresses: Port A, Port B, Port C, and a Control Port. The Port A address is always used to indicate the base 8255 address. You should give the address in hexadecimal notation by preceding it with an 'h', as in:

    DAS8JR.ADC   P:h310

Note that only the selected A, B, or C port is set to be an output... the other two ports are set as inputs. This allows other equipment to stay wired to them for other applications, since the inputs will just be ignored here. If the other application expects these to be inputs and there are active device outputs connected to them, then of course you don't want them to be forced to any possibly conflicting state.

However, suppose the other application uses those ports as outputs, and you want to leave device inputs connected to them while you run the current application. In this case, you can't assume that those device inputs will never be activated: The pins of the 8255, even though set as inputs, will have some indeterminate high or low voltage state unless they are loaded with around 5000 ohms or less. If your device inputs don't provide this load, you could be in for a nasty surprise when the other device activates unintentionally.

CAUTION:
To avoid unexpected missiles launches, third stage booster explosive squib detonation, ten-ton hydraulic ram activation, or even just a simple guinea pig food pellet dispenser cycle, be SURE to provide a few thousand ohms load to any critical device inputs that you must leave enabled but don't want to activate. Connect the load resistor from the device input to ground or +5 Volts, as appropriate to insure the desired state of the device.

When the other application later makes the port an output, it will have no trouble driving the device to either state with this "pull-up" or "pull-down" resistor present. Of course, if you are SURE that your device inputs already provide adequate loads, go ahead and skip the resistors...

USING AN LPT PRINTER PORT FOR DIGITAL STIMULUS OUTPUT:

    DAS8JR.ADC   P:Ln

If the LPT 'n' value is not in the range of 1 to 4, Daqarta will exit immediately with:

    'LPT value out of range.'

Most computer systems come with a single standard printer port, and if you need more than that you will have to install a separate board. All DOS systems can support ports LPT1 through LPT3 "naturally", without special software. The system BIOS keeps a record of the location of each LPT that it recognizes, and that record is consulted to validate the LPT value that you use here. If there is no entry for the LPT number you give (L:3 in this example), Daqarta exits with a message like:

 'LPT3 not recognized by BIOS.'
 'BIOS recognizes only LPT1 to LPT2.'

Problems may be due to adding a new printer port board and getting the jumpers or switches wrong. Most boards allow designation as LPT1 or LPT2. If you need to add LPT3, be sure the board allows it before you buy. Some boards allow LPT4 use, but not all systems support this. For example, IBM PS/2 systems use the LPT4 location in the BIOS data area for other purposes.

You can use the LTEST.EXE utility supplied with Daqarta to see the port addresses corresponding to each LPT, as read from the BIOS data area just like this driver does. A typical display would be:

  Printer Port assignments:
     LPT1: 0378h
     LPT2: 0000h
     LPT3: 0000h
     LPT4: 9FC0h

Even if LTEST shows that the LPT4 location is available to install a new port, you may need to run special software (supplied with your port board) to make use of it... not all BIOSes will assign this automatically on start-up.

S: SPEED:

This value is used as a limit when setting sample rate under menu control, and is only there as a safety net to prevent you from setting the rate so high that you get bad data. Although no DAS8JR boards are known to convert anywhere near as fast as the 5 microsecond parameter limit at present, board makers and ADC chip makers are continually working to increase speeds.

So how do you determine when you are sampling too fast for your converter? The best way is to use a known input waveform and just keep increasing the sample rate. You will get to a speed where the waveform begins to get noisy and spiky. In RTime mode you may find that you can't run as fast as in Sequential mode... be sure to test both.

Also, in RTime mode if you adjust the sampling rate to get the fastest setting that just eliminates spikes, you may find that the spikes reappear on each keystroke unless you slow the sample rate a lot more. You may want to avoid operating in this "twitchy" range for normal work, but it can be used if you are aware of the limitations and don't use any keystrokes during averaging or DDisk recording, for example.

Since the DAS8JR-family boards have no built-in pacer timers, sample timing resolution is in multiples of the main system timer resolution of 0.838 microseconds.

For example, a typical 386DX40 system in Sequential mode could run at a sample period equal to the full rated 25 µsec ADC conversion speed, but the timer resolution allows only 25.143 µsec (39.773 kHz sample rate) because the next step at 24.305 µsec is too fast for the ADC. In RTime mode on this same system, even 25.143 µsec is a bit too fast, but the next slower step of 25.981 µsec is fine... as long as no keys are being hit. Sample periods of around 36 µsec or more (27.7 kHz or lower sample rates) are needed to insure that there are no spikes during keystrokes in RTime mode.

If you use stimulus oversampling (Stimulus Generator Factor greater than 1), you may be able to have the effective stimulus output rate exceed these limits, because the outputs can run faster than the ADC. Daqarta refers to this as "Hypersampling". The DAC limit is specified at 100 kHz, but you may even be able to go beyond that. If you have a fast system and want to push your DACs to the limit, you might want to check the output waveform with an external oscilloscope, if one is available, to allow you to see spurious spikes that may be too brief for the ADC to detect when viewing the waveform with Daqarta.

On the 386DX40 system in Sequential mode, a single DAC output runs fine up to about 149 kHz. With both DACs active, the maximum is reduced to about 119 kHz... an aggregate output of 238 kHz while still maintaining input sampling. You can reach these limits by various combinations of base sample rate and Stimulus Factor:

 One DAC channel, Sequential mode:
     ADC Rate  x  Factor  =  DAC rate
     18.664 kHz     8        149.15 kHz
     29.830         5        149.15
     37.287         4        149.15

 Both DAC channels, Sequential mode:
     19.887         6        119.32 (each)
     39.773         3        119.32 (each)

 One DAC channel, RTime mode:
     ADC Rate  x  Factor  =  DAC rate
     19.887 kHz     4        79.55 kHz

 Both DAC channels, RTime mode:
     19.887         3        59.66 (each)

    'Sample rate overrun!'

Digital outputs can usually go quite a bit faster than DACs. For example, with a Stimulus Factor of 10 on the 386DX40 system mentioned above, you can generate digital outputs at a sample rate of 19.887 kHz in Sequential mode, giving a digital output sample rate of 198.87 kHz.

SPECIAL NOTES FOR 16-BIT MODELS:

Unless triggered operation is really needed for your application, you should toggle Trig off and use the resulting Free-run mode instead. You will also need to be in RTime mode, allowing overlap operation. Now the trace will update on nearly every sample, and waveforms will seem to scroll slowly across the screen from right to left. The most recent data will always appear at the right end of the trace, so you can see any changes immediately.

You are still getting only one complete new trace per 15+ seconds, but at least you can see what's happening in the meantime. When spectra are viewed, they will respond continuously but slowly to changes. For example, if there is a sudden jump in the frequency of an input tone, you will see the original peak melt away and a new one grow... the whole process again taking the same 15+ seconds.

Despite the sluggish 16-bit ADCs on these models, the 16-bit DACs on the AO versions are still capable of 100 kHz operation just like the faster 12-bit models. To make use of this speed you will need to use large Stimulus Generator Factor settings.

For example, to reach 100 kHz in Sequential mode when the ADC rate is 33 Hz, you need to set Factor to 3030. This means that the samples in the stimulus buffer are consumed 3030 times faster, so with the maximum buffer size of 64 Kbytes and a single DAC channel active (two 8-bit bytes per 16-bit sample), the total stimulus lasts less than 0.33 seconds... just the first 10 ADC samples!

And in Sequential mode, the stimulus repetition rate is limited by the time to acquire each sweep, so here you would only get one stimulus every 15+ seconds at best.

In RTime mode, however, the stimulus buffer recycles over and over endlessly, so the stimulus duration and repeat cycle are the same... in fact the problem here may be that stimuli come too often: In the above example, the SLOWEST stimulus repeat rate would be 3 per second. To go faster, just use shorter stimuli. The "off" time between stimuli is created by means of the stimulus Start delay time.

One caveat here: The sensitivity of the overrun detection system is reduced by large stimulus Factors in Free-run RTime mode, so if you set Factor too large for your system you may get s-l-u-g-g-i-s-h keyboard response without tripping the overrun detector. The stimulus and data will be unaffected, and it's OK to run like this if you really need to, but you will have to watch every keystroke to make sure it's accepted before you hit the next key.

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