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PDF ELM624 Data sheet ( Hoja de datos )

Número de pieza ELM624
Descripción Control L (LANC) to RS232 Interpreter
Fabricantes ELM Electronics 
Logotipo ELM Electronics Logotipo



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ELM624
Control L (LANC) to RS232 Interpreter
Description
The Control L or LANC interface is an industry
standard introduced by the Sony Corporation for
controlling audio and video devices. It uses a bit
serial data format, and requires that the controller be
synchronized to the controlled device – something
which is difficult to do using standard serial
interfaces. The ELM624 is an 8 pin integrated circuit
that performs the synchronizing function for you.
All user interaction with the ELM624 is by
standard ASCII characters over an RS232 interface.
There is no special formatting required, other than
perhaps an understanding of the hexadecimal
numbering system, nor is there a need for a powerful
PC - virtually any model with a serial port will do.
Since the ELM624 was designed to provide a
cost-effective way for people to experiment with the
Control L system, many features typically found in
commercial devices, such as RS232 handshaking,
variable baud rates, extra buffering of signals, etc.
have not been implemented. Responses are kept to
a minimum as well (eg. a single question mark is
returned for a misunderstood command), but the
general principles of operation are demonstrated
and for many applications, this is all that is required.
Applications
www.DataSheeVt4idUe.coomeditors
• Time-lapse recording controllers
• Programmed control of A/V equipment
• Remote camera controls
Features
• Low power CMOS design
• Enable input allows control of multiple devices
• Configurable with simple AT commands
• ASCII output formatted as standard hex digits
• Oscilloscope trigger pulse output
• Power control pulse output
• Crystal controlled for timing accuracy
• Works with 50 Hz and 60 Hz systems
• Power up to monitor mode
Connection Diagram
PDIP and SOIC
(top view)
VDD 1
XT1 2
XT2 3
Enable 4
8 VSS
7 LANC
6 Tx
5 Rx
Block Diagram
3.58MHz
XT1 2
3 XT2
VDD
Enable 4
Control
VDD
Rx 5
Tx 6
RS232
Interface
Control L
Interface
7 LANC
VSS
ELM624DSD
Elm Electronics – Circuits for the Hobbyist
< http://www.elmelectronics.com/ >
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ELM624 pdf
ELM624
AT Commands
The ELM624 can accept internal configuration
commands at any time, in much the same manner that
modems do. Any command sent to the ELM624 which
begins with the letter ‘A’ followed by the letter ‘T’ is
assumed to be an internal configuration (or ‘AT’)
command. These commands are executed upon
receipt of the terminating carriage return character,
and are acknowledged with some form of response,
which may be as simple as the characters ‘OK’.
The ELM624’s factory default settings should be
appropriate for most applications, but some users may
wish to customize their settings, such as turning the
character echo off, or perhaps quiet mode on, by
issuing these commands. Doing this is as easy as
sending AT E0, or AT Q1, followed by the return
character. Note that this version of the ELM624 is only
able to accept one command per line, so changing
multiple settings requires one line for each change.
The following summarizes the ‘AT’ commands that
are recognized by this version of the ELM624. Note
that the character ‘0’ is the number ‘zero’:
2D [ use version 2 Defaults ]
This command is used to set several of the options
to their default (or factory) settings, as if this were a
v2.x IC. In the 2D mode, linefeed characters are not
sent automatically after each carrige return, and
there is no prompt character generated when the IC
is ready to accept the next command. Other than
that, the E, C, D, Q and R options are set the same
as those discussed here for the v3.0 IC.
C0 and C1
[ send all (0) or only Changes (1) ]
These commands specify when the Control L status
bytes are to be returned on the RS232 bus. With the
www.DataShCe1et4cUo.mcommand, values are only sent when there is a
change from the previous eight bytes, while with C0
the response bytes are always sent. For most
devices, setting C1 will have little noticeable effect,
as the LANC responses usually alternate between
status and time-code values, so they do continually
change. The default is C1, send on change.
CS [ Check Sync ]
This command is used to determine (check) if the
connected LANC device is sending synchronizing
signals or not. If the signals are correct, a ‘SYNC
OK’ message will be returned. If there is a problem,
either ‘NO SYNC’ or ‘SYNC ERROR’ will be
returned. This provides a quick way to see if a
device is powered and ready to accept commands.
D [ set all to Defaults ]
This command is used to reset the E, C, D, L, Q, and
R options to their default (or factory) settings, as
when power is first applied. It provides a fast and
efficient way to restore the settings without having to
wait through the time delay of a power up reset.
D0 and D1
[ Duplicate off (0) or on (1) ]
While the LANC message structure allows for four
command bytes to be sent, most devices only use
the first two, and ignore the others. For convenience,
the ELM624 can be provided with either two or four
bytes to send, but if it is provided with only two, it
needs to know what to insert into the other two
positions of the four byte command field.
If the duplicate option is turned on, the two command
words that were provided to the ELM624 will be
inserted into the word 0 and word 1 positions, and
then will be duplicated and used for the other two
positions (words 2 and 3). If the duplicate option is
off, no duplication will occur, and 0’s will be sent in
positions 2 and 3 instead. Setting the duplicate
option to off may be useful if you suspect that a
unique device is providing status bytes in positions 2
and 3 and you do not want to overwrite them. The
default setting is D1, duplicate on.
E0 and E1
[ Echo off (0) or on (1) ]
These commands control whether all characters
received on the RS232 port are retransmitted (or
echoed) back to the host computer. To reduce traffic
on the RS232 bus, and perhaps simplify some
computer software, users may wish to turn echoing
off by issuing E0. The default is E1, echo on.
ELM624DSD
Elm Electronics – Circuits for the Hobbyist
< http://www.elmelectronics.com/ >
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ELM624 arduino
ELM624
Talking to Your LANC Device (cont’d)
looked something like these:
06122458
06324911
06420100
Comparing this to the other response, you can see
that the device is now in play mode (06), with the
time/counter still reading 00:01:11:49, as it has just
begun to play the tape. The 8 in the last position of the
first row indicates that (for this camera), there is a
‘memory mark’ here to show a significant spot on the
tape. This is how you would generally control a device
through LANC using computer control - issue a
command then monitor the status bytes until the
desired change has occurred. This way you can be
sure that the command was understood. Of course, if
you are manually controlling it from the keyboard, you
will know when the device has responded.
It is beyond the scope of this document to detail
the Control L standard in any more detail, but hopefully
this has been enough to get you started, and has
generated some ideas.
Talking to Many ELM624s - Using the Enable
The ELM624 provides an Enable input that can be
used to control whether the ELM624 pays attention to
the RS232 bus or not. This means that several devices
can share one data ‘channel’, while only those chosen
to do so will respond. In this way, controlling many
devices is not much different than controlling one,
except for the work involved in selecting the
appropriate ELM624, and deselecting the others.
RS232 data received at the Rx pin of the ELM624
www.DatawShheileet4tUh.ecomEnable input is high will be used by the IC,
and any data that appears at that pin while the Enable
is low will be ignored. You can use this in order to
selectively send information to several devices that
share a common RS232 bus. The messages sent to
each device do not have to be sent all at once as a
complete string - you can send one byte to device 1, a
few bytes to device 2, a byte to device 3, etc., as long
as you return back to each device before their internal
20 second timer causes an abort on an incomplete
string receive. This is usually quite easy to do.
To ensure that the enable works properly when
sending commands to the ELM624, be sure to have it
at an active level before the RS232 byte’s start bit
begins, and maintain it at that active level until at least
the end of the stop bit. There is no such restriction for
controlling the ELM624’s Tx output. The IC will turn the
output line off within one bit time of the Enable going
inactive, so if you do not want to receive any more
from that device, simply bring the Enable line low.
The (continuous) flow of status messages can be
monitored periodically while doing other tasks through
the Enable control. For example, one could issue a
command to rewind the tape (10 36), then periodically
check for a ‘tape end stopped’ status byte (72) while
doing other functions with other devices. There is no
restriction on how often one uses the Enable input – a
typical system with several devices will naturally try to
poll each device as often as it can to maintain ‘real-
time’ control. One should keep in mind that commands
typically take about 100 msec to complete, however,
so attempting to poll a device more often than that
may not be of much benefit.
Providing an Enable input simplifies the interface
circuitry needed if controlling multiple devices, often
reducing your design to basically a channel selector,
and one ELM624 per channel. The Example
Applications section provides a sample circuit showing
one possible way of controlling three devices through
one RS232 interface.
ELM624DSD
Elm Electronics – Circuits for the Hobbyist
< http://www.elmelectronics.com/ >
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