MIR PUBLICATIONS COMPACTUS (LENDLNG SECTION) DEPARTMENT OF NATIONAL RESOURCES 066770 NATIONAL DEVELOPMENT ill BUREAU OF MINERAL RESOURCES, • GEOLOGY AND GEOPHYSICS 1979/48 SIXTEEN CHANNEL DIGITAL MULTIPLEXER BMR type XMM-1 A.B: DEVENISH The information contained in this report has been obtained by the Department of NationUI Resources srt of the policy of the Australian Government to assist in the exploration and development of .al resources. It may not be published in any form or used in a company prospectus or statement put the permission in writing of the Director. Bureau of Mineral Resources, Geology and Geophysics. •
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MIR PUBLICATIONS COMPACTUS(LENDLNG SECTION)
DEPARTMENT OFNATIONAL RESOURCES
066770
NATIONAL DEVELOPMENTill BUREAU OF MINERAL RESOURCES,
•GEOLOGY AND GEOPHYSICS
1979/48
SIXTEEN CHANNEL DIGITAL MULTIPLEXER
BMR type XMM-1
A.B: DEVENISH
The information contained in this report has been obtained by the Department of NationUI Resourcessrt of the policy of the Australian Government to assist in the exploration and development of.al resources. It may not be published in any form or used in a company prospectus or statementput the permission in writing of the Director. Bureau of Mineral Resources, Geology and Geophysics.
•
1979/48
SIXTEEN CHANNEL DIGITAL MULTIPLEXER
BMR type XDM-1
A.B. DEVENISH
•
•
Contents
•
•1. Introduction
2. Functional Descri -otion
3.^Unit Description
(i) Block Diagram
(ii) Tri-State Bus
(iii)Latch
(iv) Unit Select
(v) Channel Select
(vi) Busy
(vii) Device Flag
(viii)Power Supply
(ix) Bus Buffer
(x) Card Types
(xi) Software testing
(xii)Daisy Chaining
4.^Specifications
5. Use in VH-BMR aircraft
6. Use in magnetotelluric system
7.^Drawings and handbooks
(i) Circuit Schematic of Data hatch
(ii) Circuit schematic of Channel Select
(iii)Circuit Schematic of Bus Buffer
(iv) Circuit schematic of power supply.
• -
•
•
1. Sixteen Channel Digital Multiplexer
BMR Type XDM-1
1. Introduction
The HP 2100 series computers used for survey data acquisition
have nine input/output slots, some of which are used for such peripherals
as teletypes and tape units. Normally, each device outputting data to
the computer would require one input/output slot, which limits the number
of devices which could be connected to the computer. This problem can be
overcome by multiplexing a number of digital inputs into the one input/output
slot.
A decision was made by the ADP and Electronics Sections to design
a 16-channel 16-bit word multiplexer for use with the HP 2100 series
computers. Two units were constructed inihe first instance, one for thecomputer-based data acquisition system in BMR's Aerocommander survey
aircraft, the other for BMR's magnetotellurics system. The unit in the
survey aircraft inputted the altitude, 4 gamma-ray channels, magnetometer
readings, fiducial numbers and flight numbers. The unit in the magnetotelluric
system inputted the gain and filter settings of the E pre-amps, the H pre-amps,
and the post-amps. Some of the inputs from the magnetotelluric system
required voltage level translation to TTL. To allow for this, the option
of optically isolating each input was incorporated.
Three units have been constructed. Units have been used in the
Aerocommander survey aircraft and in the magnetotelluric system. Other units
will be used in the Twin-Otter aircraft and in the marine data acquisition
system to expand its input capacity to 32 channels.
2.
2. Function Description
The function of this unit is to receive 16-bit parallel
inputs from various input devices and output them, one 16-bit channel
at a time, to a HP 2100 series computer. There is a maximum of 16 input
channels, and a digital channel-select output from the computer determines
which input the computer will receive.
Up to eight units can be 'daisy chained' together to expand the
input capacity to 128 channels.^ •
The multiplexer provides for a busy device input which, if
activated, will disable the inputs to its internal latches.
Any one channel, and only one, can be linked to set the flag of
the computer I/O card.
All imputs and outputs are TTL compatible; the inputs may be
optically isolated.
DEVICE BUSY AND FLAG
16 INPUT CHANNELS.
(16 BI TS PERCHANNEL)
AS ABOVE
AS ABOVE
.-111110---DEVICE FLAG-0.---UNIT SELECT^(4 BITS)
MULTIPLEXER ^CHANNEL SELECT(4 BITS)DATA (16 BITS)
TO /0CARD IN
COMPUTER
MULTIPLEX ER
INTER-MULTIPLEXER CONNECTION
MULTIPLEXER
3. Unit Description
(I)^BLOCK DIAGRAM:
16 DECODE LINES_ONE FOR EACHCHANNEL.
OPTO- ISOLATORS. BUFFEREDLATCH.
8 BITS TO NEXT CHANNELAND UNIT SELECT.
3 .
•
(Note: The input data may be directly connected or optically isolated
from the data latches. If directly connected, the opto-isolators
are removed from their sockets and links put in.)
• (ii) Tri-State Bus
The outputs of all latches •in all units are connected to the
data bus. Which sixteen bits of data are valid on the bus depends on
which set of four latches is enabled by the channel and unit select
inputs.
4 .
4 BITSLATCH
16 DATA BITS
LATCH
ENABLE
4 BITSIIP^
4 BITSLATCH
LATCH
(iii) Latch
The input data for all channels are latched to the output by
means of a latch pulse. The latch pulse is generated in the computer by
the instructions:
STC^mpx
CLC^mpx
(iv) Unit Select
Bits 4-7 from the computer are used to determine which unit is
to be selected. A link has to be connected in the channel select card to
make the unit correspond to the chosen bit pattern. The unit select
decoder enables the channel select decoder for that unit.
(v) Channel Select
Bits 0-3 from the computer are used to select which output
channel is enabled onto the data bus.
( vi) Busy
The multiplexer may accept a busy signal from a device. This
signal disables the input to that device. If the busy channel is enabled,
only the previous stored reading of the input device will be put onto the
data bus.
41
DATA
BUS
4 BITS
5 .
(vii) Device Flag
41^ Any one device may be chosen to set the flag of the computer.
This is accomplished by installing a link on the appropriate data latch
card. Provision is made for selecting either logic state of the signal
41^input on the device flag line.
(viii) Power Supply
41^ Three types of power supply have been used in the multiplexers.
A 28 volt D.C. to 5 volt D.C. switching regulator type for aircraft use,
a 115 volt (50-400 Hz) A.C. to 5 volt D.C. for the magnetotelluric system, and a
41^standard 240V (50 Hz) A.C. to 5 Volt D.C. for other users.'
(ix) Bus Buffer
•^The data bus is buffered to the computer using open collector
buffers .. The device command signal from the computer is buffered by a
transistor to strobe all the data latches.
(x) Card Types
The unit contains 3 card types. They are:
(a) Channel Select card - This card enables the selected channel by
enabling the output onto the bus.
0^(b) Data latch card - Each of these. cards receives 16 data inputs
• from a device.. One of these cards is required for each device
• being multiplexed. The data inputs can either be direct or
optically coupled. For direct'coupling, the optc isolators are
removed from their sockets and wire bridges put in their place.
• (c) Bus buffer card - This card buffers the data bus going to the
•^computer and the device command 'signal going from the computer
to the device.
(Note: Cards have their card types Written on them).
6 .
(xi) Software Testing
The multiplexer can be tested by inserting a small program into
the computer and putting a known input into the various data inputs.
INPUTDATA
CPU
!MULTIPLEXER
A suitable program would be
START^LDA^X^Load the A register with memory
location X.
OTA^mpx^Output the A register to the select
code used with the multiplexer.
STC^mpx^These two instructions cause the latches
CLC^mpx^to strobe the input data.
LIB^mpx^Load the B register with what is on the
bus.
OTB^1^Output the B register to the switch
register.
JMP START^Jump back to start.
mpx is the select code of the I/O card used.
Memory location X^
7-4^3-0
unit select channel select
(xii) Daisy Chaining
The data bus, latch drive, device flag and lines for channel
select and unit select go to two other connectors to enable 'daisy
Chaining' of units.
INPUTS
CPU
4
MULTIPLEXER
MULTIPLEXER
INPUTS
7.
Up to 128 inputs may be on the data bus. This upper limit is due to the
electronic specifications of the tri-state latches.
Specifications
•-^Weight^-^6 kg
Size^-^24 x 9 x 48 cm
Supply voltage -^28 volt D.C.^4A max or 115V (50-400 Hz)
•^ A.C. or 240V (50 Hz) AC
Inputs^16^16 parallel bit data inputs.
TTL compatible.
busy line.
device flag.
Note: All inputs may be optically isolated. If the opto-isolators are
• used, the common line (Pin 1B) is taken to the logic high of the
device. If the opto-isolators are not used, the normi ground is
used as the logic common (Pin 24). The opto-isolators have to be
• removed and the following bridge put in.
8765
•1234
Outputs^ multiplexer/multiplexer connections.
data out to + ve true I/0 card.
•
•
1 11 11 11 1 1111 1111rn^_____
Mu ILI e xerti-Multiplexer
'Channel 0
Connector positions
8 .
Rear Panel
,^16 Inputs
5.^Use in VH-BMR aircraft
The multiplexer is used in the survey aircraft system to connect
nine input channels to one computer I/O slot.
CHANNEL SELECTUNIT SELECTAND STROBE
CPU
MULTIPLEXER
I I ,1-
FLIGHT NUMBER
SCALERS( RADIOMETRIC COUNT)
FIDUCIAL NUMBER
ALTITUDEDIGITIZER
I MAGNETOMETER
DATA OUT 15 14 13 12 11 1098 765 432 10
0
9 .
•Channel. Select, Unit Select and input device correspondence
• Device^ Channel^Select^Unit Select
Magnetometer most significant digit^o
Magnetometer four least significant
digits
Altitude^ 2
• Fiducial Number^ 3
• Radiometric 1^ .4
0-^Radiometric 2^ 5
Radiometric 3^ .6
Radiometric 4^ 7
Flight number^ 10
6.^Use in the Magnetotelluric system
• The magneto—telluric data acquisition system records the 3 orthogonalmagnetic field components (11z,RX,Fry) of the electromagnetic radiation impinging onthe earth's surface and two -^, : resulting orthogonal electric field
components Ex,Ey) at the earth's surface.From these data the magneto—telluricparameters Cagniard resistivities t rotated resistivity tensors and phase anp:les,etc) are computed.•
In order to recover the actual values of these related fields
it is essential to correct the measurements using the transfer•characteristics of the amplifiers and filters used in making the
.measurements.
To do this the gain and filter settings are encoded and passed to
the multiplexer which outputs them to the computer. The computer then
stores them with the relevant measurements for subsequent correction.
•10.
GA IN AND FILTER SET Tti GS
4110---111111-
•MUX
CPUSTORAGE
DISC
PRE-AMP POST-AMPAND AND ADC •
FILTER FILTER
Channel Select, Unit Select and input correspondence
Device^ Channel Select Unit Select •Pre-amp gain and filter settings^Ex,Ey^optically
isolated
0 0
Hz,Hx,Hy optically
isolated
1 0 -•
Post-amp gain And filter setting 23 0 •4
Computer flag 5
7.^Drawings and Handbooks ^ •Four circuitschematics can be found in the back of this record.
The circuits are
Data Latch
Channel Select
Bus Buffer
Power Supply^ •
The 28 volt to 5 volt switching regulator is incorporated in the
unit used in the survey aircraft. The circuit diagram for it is given. •The units which run off 240 and 115 volt A.C. use commercial modular power
supplies.
•
•
0 -
•
•
•
The handbooks for the unit contain parts lists and wiring lists
as well as circuit diagrams.
Handbooks can be found in the handbook master copy library in the
Enqineoring Serv 4_ces Branch and with each of the user groups,
•Printed by C. J. Thoupsom. Commonwealth Government Printer, Canberra