



      ADC12.DOC         MVS Box 850 Merrimack,NH          3/20/94




HARDWARE
--------

The ADC12 card is a sixteen channel 12-bit Successive Approximation type
Analog to Digital Converter.  Maximum sample rate is 100 khz.  Two of the
channels have sharp cutoff low-pass filters for signal conditioning and
noise reduction.  A 10 volt precision voltage reference is available for use
with external circuitry.  Three TTL compatible output bits are provided for
control of relays, indicators, and other devices.

The ADC12 input voltage range is -2.5 to +2.5 on channels A-B which are
filtered and -5.0v to +5.0v on channels C-H.  0 volts reads as 8000h.  The
lowest value reads as 0000h and the highest reads as FFF0h.  Higher
voltages can be read with the use of external resistive dividers as long as
the voltages actually applied to the ADC are within the input range.  In
any case voltages exceeding -5.5 to +5.5 volts can damage the device.

A sample and hold function provides for improved fidelity in audio
applications and rapid sampling for data acquisition.

Dual 2-pole active filters improve record quality in stereo audio
applications and allow longer cables when used for data aquisition.  Cutoff
frequency is approximately 22khz and the gain is 2.  The filters invert and
convert plus/minus 2.5v to the -5v to +5v range that the ADC expects.  The
filtered channels accept industry standard line levels (0dbm 2.2vpp 600ohm)
with a little headroom to spare.  Lower voltages such as microphone signals
can be read if external amplification is used.

A special version with an input range of 0-10v is available (ADC12b).  Only
8 channels are provided (A-H) and no lo-pass filter is used.  0 volts reads
as FFF0h and 10 volts reads as 0000h.  In this version the maximum input
-.5 to +10.5 volts.  Another special version is available (ADC12d) that has
8 differential inputs instead of 16 single.




SOFTWARE
--------

The Control Register has three channel select bits and two MPX enable bits. 
10h-17h selects channels A-H and 08h-0Fh selects channels I-P.  It is a
good idea to wait a few microseconds for the multiplexer to stablize before
starting conversion.  One trick is to switch channels for the next
conversion before reading and processing data from the previous cycle.

Conversion is started by reading the Start Conversion Address.  The result
is available via the Read Data Addresses no sooner than 10 microseconds
later.  12 bits are read as two separate 8 bit bytes (MSB and LSB).  The
lower 4 bits of LSB are always 0 which eliminates bit masking instructions
and allows for software compatibility with 16 bit converters.

ADC12C is a demo program showing how to use the ADC12 with Turbo C.  It
displays input voltages on all sixteen channels continuosly as hex words. 
To simplify readings the unused lower 4 bits are discarded.  The code can
be run on a PC or the MVS Single Board Computer with proper modification. 
Read the source file, ADC12C.C, for more detailed information.

TTL outputs are available as three bits of the Control Register.  This
register also contains the multiplexer channel selection.  Remember to
properly mask bits when doing both operations to avoid interference.




SPECIFICATIONS
--------------

Electrical:

Supply Voltage: -4.5 to +5.5, +-11.4 to +-13
Supply Current: 20ma at 5v, 10ma at 12v
Resolution: .024%
Maximum Sample Rate: 100khz
Maximum input voltage to avoid damage: ADC12/ADC12d +-5.5, ADC12b -.5 +10.5
Impedance of circuit supplying input voltages: 75ohm
Signal to Noise and Distortion: 70dB
Total Harmonic (THD) and Intermodulation (IMD) Distortion: -90dB
S/H Aperture Delay: 15ns
S/H Aaperture Jitter: 150ps
S/H Acquisition Time: 1us


Physical:

Size: 3.2"x4.2"x0.5"  
Temp: -20 to 70C   
Humidity: 0-95 percent non-condensing    
Vibration: 10-60Hz 2mm pp


Block Diagram:

  ADC B in----------,
  ADC A in -----,   :
                :   :               ,-------,    ,-----,   PC BUS
      ,------,  :------Filt A out-->:       :    :     :    :
      : FILT :  :   :--Filt B out-->: DUAL  :--->: ADC :--->:
 IN-->:  A   :--'   :   ADC C in--->:   8   :    :     :    :
      :      :      :   ADC D in--->: CHAN  :    '-----'    :
      '------'      :   ADC E in--->:  MPX  :               :
                    :   ADC F in--->:       :       ,----------,
                    :   ADC G in--->:       :       :          :-->TTL A
      ,------,      :   ADC H in--->:       :       : CONTROL  :-->TTL B
      : FILT :      :                -------        :          :-->TTL C
 IN-->:  B   :------'   ADC I in--->:       :<------: REGISTER :
      :      :          ADC J in--->:       :       :          :
      '------'          ADC K in--->:       :       '----------'
                        ADC L in--->:       :
 Filters not available  ADC M in--->:       :
  on ADC12b or ADC12d   ADC N in--->:       :
                        ADC O in--->:       :
                        ADC P in--->:       :
                                    '-------'


I/O Connector pinout:

  1 Ground         2 NC           
  3 Ground         4 NC              ADC Registers:
  5 Ground         6 Filter A in    Start Conversion    = 260h  
  7 Ground         8 Filter B in    Read 8 MSB as d7-0  = 262h
  9 Ground        10 ADC C in       Read 4 LSB as d7-4  = 263h
 11 ADC E in      12 ADC B in       Control Register    = 264h:
 13 ADC G in      14 ADC A in           D0=MPX Bit 0   D4=Enable A-H
 15 ADC H in      16 ADC D in           D1=MPX Bit 1   D5=TTL out A
 17 ADC F in      18 ADC K in           D2=MPX Bit 2   D6=TTL out B
 19 ADC M in      20 ADC J in           D3=Enable I-P  D7=TTL out C
 21 ADC O in      22 ADC I in     
 23 ADC P in      24 ADC L in       Address Range Jumpers:
 25 ADC N in      26 10v Ref out      160-17Fh = J1-J5 2-6 3-7 4-8
 27 Ground        28 TTL A out        1A0-1BFh = 1-6 2-5 3-7 4-8
 29 TTL B out     30 TTL C out        260-27Fh = 1-5 2-6 3-8 4-7*
 31 Ground        32 VCC out          2A0-2BFh = 1-6 2-5 3-8 4-7
 33 -12v out      34 +12v out         320-33Fh = 1-8 2-6 3-7 4-5
                                            *default


Board Layout:

              pin 1          pin 33
      ,-----,  |||||||||||||||||||  ,-----,
      :  O  :  :      I/O        :  :  O  : mtg holes for 6-32
      :     '--'                 '--'     :   standoffs
      :                                   :
      :                                   :
      :                                   :
      :                                   :
      :                                   :
      :                                   :
      :        View from Component Side   :
      :                                   :
      :                                   :
      :                                   :
      :                                   :
      :                                   :
      :     J1  J4                        :
      :      oooo                         :
      :  O   oooo                      O  : mtg holes for 6-32
      :     J5  J8                        :   standoffs
      :                 PC Bus            :
      |||||||||||||||||||||||||||||||||||||
     pin A31                          pin A1


Mounting:
                                   
The ADC12 is often used with inexpensive PC motherboards and an MVS ROM
Drive for embedded applications or portable computers.  Using a right angle
PC Bus Expander (part number BP4) allows cards to lie down flat. 
Everything can now fit in a compact low-profile case.

The ADC12 has the same form factor as the MVS Single Board Computers. 
Corner holes are in the same position which simplifies mounting with
standoffs.  The PC Bus end of the ADC12 and the SBC are connected with a
passive backplane.  This can be done constructed using 62 pin IDC
connectors (part number MVCON1) and a short length of ribbon cable.  If a
circuit board type passive backplane is needed then use BP4.  Other PC
adapter cards can be added on in the same way.

                         LIMITED WARRANTY 

MVS will repair free of charge product suffering from manufacturing defects
for a period of 5 years after shipping.  This will be done only if it has
been determined by MVS that the product has not been misused (improper
voltages, physical alteration, etc.).  Otherwise a minimum service charge
is required.  In either case it is necessary to contact MVS for a Returned
Merchandise Authorization (RMA) number before shipping the unit.

