Alcorn Mcbride 1756-Show I/O User manual

1756-Show I/O
User’s Guide
by Alcorn McBride Inc.

Document Revision 1.0
October 2003
Copyright 2003 Alcorn McBride, Inc. All rights reserved.
Every effort has been made to assure the accuracy of the information contained
in this manual, and the reliability of the hardware and software. Errors
sometimes can go undetected, however. If you find one, please bring it to our
attention so that we can correct it for others.
Alcorn McBride Inc. reserves the right to make changes to these products,
without notice, in order to improve their design or performance.
Applications described herein are for illustrative purposes only. Alcorn McBride
Inc. assumes no responsibility or liability for the use of any of these products,
and makes no representation or warranty that the use of these products for
specific applications will be suitable without further testing or modification.
Our Show Control equipment is not intended for use in applications where a
malfunction can reasonably be expected to result in personal injury or damage to
equipment. Customers using or selling Alcorn McBride Inc. products for use in
such applications do so at their own risk, and agree to fully indemnify Alcorn
McBride Inc. for any damages resulting from such improper use or sale.
The 1756-Show I/O incorporates technology which is licensed from Allen-
Bradley Company, Inc. Allen-Bradley has not technically approved, nor does it
warrant or support the 1756-Show I/O. All warranty and support for the 1756-
Show I/O and its application is provided solely by Alcorn McBride.
ControlLogix and RS-Logix5000 are trademarks of Allen-Bradley/Rockwell
Automation, Inc.
Product Design: Jeremy Scheinberg, Jim Janninck.
Documentation: Jeremy Scheinberg, Jim Janninck
Alcorn McBride Inc.
3300 S. Hiawassee, Suite 105
Orlando, Florida 32835
[phone]
FAX: [phone]
http://www.alcorn.com
[email protected]

Contents
Welcome 1
What is SMPTE Time Code?.....................................................................................................1
Technical Support ......................................................................................................................2
Installing the 1756-Show I/O 3
Setting the SMPTE Output Level...............................................................................................3
Module Power Consumption......................................................................................................3
Installing the Module in the ControlLogix Chassis....................................................................4
Wiring the Module.....................................................................................................................4
Module Pinout............................................................................................................................6
Module I/O 7
Module Configuration................................................................................................................7
Output File .................................................................................................................................9
Input File..................................................................................................................................10
Using the Module as a SMPTE Generator 11
Generator Theory of Operation................................................................................................11
Configuring the Generator .......................................................................................................12
Controlling the Generator.........................................................................................................14
Monitoring the Status of the Generator....................................................................................15
Typical Applications & Sample Rungs....................................................................................17
Using the Module as a SMPTE Reader 19
Reader Theory of Operation.....................................................................................................19
Configuring the Reader............................................................................................................20
Controlling the Reader.............................................................................................................21
Monitoring the Status of the Reader.........................................................................................22
Typical Applications & Sample Rungs....................................................................................23
Appendix A – Module I/O Configuration Tables 25
Output –....................................................................................................................................25
Input –......................................................................................................................................26

Welcome 1
Welcome
Welcome
Since the first V16 was introduced in 1986, Alcorn McBride has been providing
high quality show control solutions to the entertainment industry. The 1756-
Show I/O module brings that same power to the Allen-Bradley ControlLogix
family of programmable logic controllers. We at Alcorn McBride are pleased to
provide you with these tools. Good luck, have fun, and thanks for choosing
Alcorn McBride!
What is SMPTE Time Code?
Think for a moment about any recorded performance. It could be a stereo
recording of a symphony orchestra, a video of your child’s birthday party, or
your favorite motion picture. It would be very desirable to know the length of
the performance, and to be able to jump in to any point in the recording
accurately. Early systems provided such capabilities by linking a mechanical
counter to the tape or film reels. By counting revolutions of the reel, one could
return to the same point in the recording repeatably, and get some sense of the
overall length of the piece.
Mechanical or electronic counters work very well. In fact, they are still in
widespread use in much of today’s audio and video equipment. However, they
do have drawbacks, such as the lack of consistency from one machine to
another, and the fact that the counts can change when the tape gets edited or
copied.
A far more accurate system would encode the time information as a part of the
presentation itself, perhaps as an additional track of a multi-track audio
recording. This is exactly the technique that was standardized in 1981 by the
Society of Motion Picture and Television Engineers (SMPTE) and subsequently
adopted by the European Broadcast Union (EBU). The complete standard was
published as ANSI V98.12M-1981, and is generally known as the SMPTE/EBU
Longitudinal Time Code, or more simply, SMPTE Time Code.
To achieve film-like editing capability, SMPTE Time Code represents time in
hours, minutes, seconds, and frames. The common frame rates are 24 frames
per second for film work, 25 frames per second for European television, 30
frames per second for NTSC black and white television, and 29.97 frames per
second for NTSC color television. A typical SMPTE readout looks like
02:28:35:15, indicating 2 hours, 28 minutes, 35 seconds, and 15 frames.

2 Welcome
SMPTE Time Code is often used to synchronize various elements of a complex
presentation. Equipment such as film projectors, video sources, audio systems,
lighting consoles, and motion controllers can read the time code to remain at the
proper point in the show at all times.
The 1756-Show I/O brings the ability to read and generate SMPTE/EBU time
code to the Allen Bradley ControlLogix family of programmable logic
controllers. The module is compatible with all processors in the ControlLogix
family, including the Logix5550 or Logix5555 processors.
Technical Support
You can obtain information about specifying, installing, configuring, and
programming your Alcorn McBride 1756-Show I/O from several sources:
For… Contact… When?…
Telephone Support [phone] M-F 9am–6pm (EST)
Fax Support [phone] M-F 9am-6pm (EST)
E-Mail Support [e-mail] Any Time

Installing the 1756-Show I/O 3
Module
Setup
Installing the 1756-Show I/O
The Alcorn McBride 1756-Show I/O plugs directly into a standard ControlLogix
chassis. The module is compatible with all ControlLogix modular processors,
including the Logix5550 and Logix5555.
Setting the SMPTE Output Level
If the module is being used to generate SMPTE time code, set the SMPTE time
code output level before installing the module in the chassis. The 1756-Show
I/O includes one eight-position switch at the edge of the circuit board, labeled
SW1, to select the output level, measured in volts peak to peak.
Switch SW1 Settings
1 2 3 4 5 6 7 8
4.0 Vpp On Off Off Off Off Off Off Off
3.5 Vpp Off On Off Off Off Off Off Off
3.0 Vpp Off Off On Off Off Off Off Off
2.5 Vpp Off Off Off On Off Off Off Off
Output Level
2.0 Vpp Off Off Off Off On Off Off Off
Module Power Consumption
The 1756-Show I/O module draws a maximum of 0.420 Amps at 5 VDC. The
module uses 0.001 Amps at 24VDC.

4 Installing the 1756-Show I/O
Installing the Module in the ControlLogix
Chassis
Installing the Module
Align the module circuit board with the card guides in the chassis.
Gently push the module in until it is firmly seated, with the retaining clips
engaged at the top and bottom.
Removing the Module
Press the retaining clips at the top and bottom of the module and slide the
module straight out of the chassis.
Wiring the Module
Attention! Never wire any module while power is applied.
The 1756-Show I/O uses a Removable Terminal Block (RTB). The module can
accommodate Allen-Bradley part number 1756-TBNH/A. The module wiring
terminals accept two wires per terminal (maximum) of 14 AWG or smaller
stranded wire. Maximum screw torque is 8 in-lb.
The module terminal block is removable. Simply unscrew the upper right and
lower left release screws and pull the entire terminal block straight out. When
replacing the terminal block, alternate the tightening of the release screws to
avoid cracking the block. Maximum screw torque is 8 in-lb.
SMPTE Input
When the 1756-Show I/O is used to read external time code, the signal is
connected to this input. The input is transformer balanced with a 600 ohm
characteristic input impedance, and can accept signals from 2 Vpp to 5 Vpp.
Connect the positive drive to the terminal labeled ‘SMPTE IN +’ (Pin 2) and the
negative drive to the terminal labeled ‘SMPTE IN -’ (Pin 4). There is no
terminal for the cable’s shield; it should be connected to the chassis ground at
the other end of the cable.
SMPTE Output
When the 1756-Show I/O is used to generate or regenerate time code, the signal
comes out of this output. The output is transformer balanced to drive a 600 ohm
load, and can output signals from 2 Vpp to 4 Vpp, as selected by switch SW1.
Connect the terminal labeled ‘SMPTE OUT +’ (Pin 6) to the positive drive and
the terminal labeled ‘SMPTE OUT -’ (Pin 8) to the negative drive. There is no

Installing the 1756-Show I/O 5
Module
Setup
terminal for the cable’s shield; it should be connected to the chassis ground at
the other end of the cable.
DMX Input
Not currently implemented. Please contact Alcorn McBride for further details.
DMX Output
Not currently implemented. Please contact Alcorn McBride for further details.
Midi Input
Not currently implemented. Please contact Alcorn McBride for further details.
Midi Output
Not currently implemented. Please contact Alcorn McBride for further details.

6 Installing the 1756-Show I/O
Module Pinout
Pin
Number Description
1 Ground
2 SMPTE Input +
3 Ground
4 SMPTE Input -
5 Ground
6 SMPTE Out +
7 Ground
8 SMPTE Out -
9 Ground
10 Midi In + (Not currently Implemented)
11 Ground
12 Midi In – (Not Currently Implemented)
13 Ground
14 Midi Out + (Not Currently Implemented)
15 Ground
16 Midi Out – (Not Currently Implemented)
17 DMX - (Not Currently Implemented)
18 DMX + (Not Currently Implemented
19 N/C
20 N/C

Module I/O 7
Module
I/O
Module I/O
All communications with the 1756-Show I/O takes place through the Output and
Input Data Files. The module can be configured manually or, for ease of setup,
you can use the .ACD file that is included on disk (or from www.alcorn.com) as
a quick reference.
Module Configuration
The 1756-Show I/O module is configured as a Generic 1756 Module. If you
are using the existing .ACD file, you can base your program from this file and
use this configuration. If you would like to configure the module manually, it is
necessary to Add a New Module All Configuration is done using
RSLogix5000.
1. Right-Click on the I/O Configuration and choose New Module…
2. Select the “1756-MODULE Generic 1756 Module” module type.
3. In the first configuration screen, enter the information as seen below:

8 Module I/O
4. In the “Connection” window, modify the “Requested Packet Interval (RPI)”
to 30.0 ms as seen below:
5. Click Finish to exit the Module Properties window.

Module I/O 9
Module
I/O
It is now possible to enter the User-Defined Data Types. To do so:
1. Expand and right-click the Data Types…User Defined tree and select New
Data Type…
2. Enter the Structure Name as 1756_SMPTE_Inputs.
3. Enter the table information as listed in Appendix A. After the information
has been entered, the size of the Input Data Type should be 8 bytes, while
the size of the Output Data Type should be 16 bytes.
4. After this information has been entered, it will be possible to build ladders
referring to the actual literal Data Type Names for the resources.
Output File
The eight words in the output file configure and control the SMPTE module.
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0 x x x x x Frame Rate Mode Mute x Loop x Set Stop Run
1 Dropout Tolerance
2 Set Hours Set Minutes
3 Set Seconds Set Frames
4 Loop Start Hours Loop Start Minutes
5 Loop Start Seconds Loop Start Frames
6 Loop End Hours Loop End Minutes
7 Loop End Seconds Loop End Frames
Module Output File
The next two chapters contain complete descriptions of the function of each
word in the Output File.
Bits marked ‘x’ are reserved for future use. They should always be set to zero.

10 Module I/O
Input File
The eight words in the input file indicate module status to the PLC.
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0 Hours
1 Minutes
2 Seconds
3 Frames
4 x x x x x Drop Gen Lock Frame Rate
5 Error Codes
6 x x x x x x x x x x x x x x x x
7 x x x x x x x x x x x x x x x x
Module Input File
The next two chapters contain complete descriptions of the function of each
word in the Input File.
Bits marked ‘x’ are reserved for future use. They are all set to zero.

Using the Module as a SMPTE Generator 11
SMPTE
Generator
Using the Module as a SMPTE
Generator
The 1756-Show I/O contains a very versatile SMPTE generator, which has been
designed for flexibility and ease of use. With this generator, one can easily
accomplish many tasks:
• Produce SMPTE time code at all common frame rates.
• Roll time code from a start point to an end point.
• Create an automatic loop of time code that will continue running without
further intervention.
• Create jumps or discontinuities in the time code.
Generator Theory of Operation
The SMPTE generator is always active in order to produce an internal frame
clock. Every frame, the time code output advances by one frame (if the
generator is running), or remains unchanged (if the generator is idling). When
the generator is idling, the output can be muted to prevent transmitting the same
SMPTE code over and over.
The generator constantly compares the SMPTE output to the user’s Loop End
Time (contained in the Output File). When the current time reaches the Loop
End time, the generator will automatically jump to the Loop Start time or halt,
depending on the setting of the Loop bit. The jump can be disabled by simply
setting the Loop Start time equal to the Loop End time. In this case, the
generator will either keep running or stop at the Loop End Time, depending on
the setting of the Loop bit.
The output time code is always available to the PLC through the Input File. The
PLC can use this information to trigger execution of rungs, or to reload the
SMPTE generator at a specific time to create a controlled jump in the time code
output.

12 Using the Module as a SMPTE Generator
The SMPTE generator follows a simple process to generate time code. Each
frame, the module performs these tasks:
1. Convert the current time to a string of 80 bits and if the generator is not
muted, send those bits out the SMPTE output.
2. If the STOP bit has changed from a zero to a one, switch the generator from
RUNNING to IDLING.
3. If the RUN bit has changed from a zero to a one, switch the generator from
IDLING to RUNNING.
4. If the SET bit has changed from a zero to a one, replace the current time
with the user’s new time code, otherwise, add one frame to the current time
if running or leave the current time unchanged if idling.
5. If the current time matches the Loop End time, replace the current time with
the Loop Start Time if the Loop bit is set (one), or switch from RUNNING
to IDLING if the Loop bit is clear (zero).
6. If the unit is idling and the MUTE bit is set, mute the SMPTE output.
7. Make the time code available to the PLC through the Input File.
Configuring the Generator
The 1756-Show I/O generator is entirely controlled by words in the PLC Output
File. See the Module I/O Space chapter for a diagram of the Output File.
Operating Mode
When the MODE bit is set (one), the module will generate SMPTE time code
internally. When this bit is clear (zero) the module will read external SMPTE
time code.

Using the Module as a SMPTE Generator 13
SMPTE
Generator
Frame Rate
The generated SMPTE frame rate is determined by this 3-bit field.
Bit 0/10 Bit 0/9 Bit 0/8
30 fps 0 0 0
29.97 fps non-drop 0 0 1
29.97 fps drop 0 1 0
25 fps 0 1 1
24 fps 1 0 0
23.976 fps 1 0 1
The other two codes (110 and 111) are reserved for future use.
Loop Start, End Times
When the SMPTE output reaches the Loop End Time, it immediately jumps to
the Loop Start Time if the LOOP bit is set, or halts if the LOOP bit is clear.
Any invalid entries, such as minutes greater than 59, will be treated as if the
entry were zero. An error bit will be set in the Input File to highlight the
problem field.
Loop Behavior
If the LOOP bit is set (one), then when the SMPTE output reaches the Loop End
Time, the generator will jump to the Loop Start Time and continue generating
from there. If the LOOP bit is clear (zero), then the SMPTE output will stop at
the Loop End Time. Notice that by setting the Loop Start Time equal to the
Loop End Time, the module can be made to generate a continuous, unbroken 24
hour long loop of time code. Also, the Loop Start Time need not be smaller than
the Loop End Time. Time code rolls over at 23:59:59:29, so the End Time will
be reached eventually.
Mute Behavior
If the MUTE bit is set (one), then the SMPTE output is muted. Time code can
continue to be generated internally, but the output does not send the code. It is
as if the cable has been unplugged. If the MUTE bit is clear (zero), then the
SMPTE output sends whatever time code is being produced internally.
Dropout Tolerance
Only the SMPTE reader uses this word. It may be set to any value when
generating time code; the module will ignore it entirely.

14 Using the Module as a SMPTE Generator
Controlling the Generator
The 1756-Show I/O generator is entirely controlled by words in the PLC Output
File. See the Module I/O Space chapter for a diagram of the Output File.
Note: The 1756-Show I/O samples the control bits once per frame. Pulses of
less than 33 milliseconds will not activate the module properly.
Setting the Current Time
Whenever the SET bit transitions from a zero to a one, the SMPTE time in the
Set Time words will be loaded into the SMPTE generator’s output. The load
occurs at the next frame edge, so the time can be altered while the generator is
running or while it is idling. Any invalid entries, such as minutes greater than
59, will be treated as if the entry were zero. An error bit will be set in the Input
File to highlight the problem field.
Starting the Generator
Whenever the RUN bit transitions from a zero to a one, the generator switches
from IDLING to RUNNING. If the generator is already running, the rising edge
on the RUN bit has no effect.
Stopping the Generator
Whenever the STOP bit transitions from a zero to a one, the generator switches
from RUNNING to IDLING. If the generator is already idling, the rising edge
on the STOP bit has no effect.