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ELM624 Schematic ( PDF Datasheet ) - ELM Electronics

Teilenummer ELM624
Beschreibung Control L (LANC) to RS232 Interpreter
Hersteller ELM Electronics
Logo ELM Electronics Logo 




Gesamt 16 Seiten
ELM624 Datasheet, Funktion
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
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ELM624 Datasheet, Funktion
ELM624
AT Commands (cont’d)
FD [ send Formatted Data ]
This command requests that all responses from the
LANC device be sent as standard ASCII characters
which are readable with virtually any terminal
program. The four status bytes (words 4, 5, 6 and 7)
will be sent as eight hexadecimal digits, with two
ASCII characters representing each byte. There is
insufficient time at 9600 baud to insert spaces to
separate these bytes, so they are simply sent as a
block of eight characters. Every line will end with a
carriage return character and (optionally) a linefeed
character, ensuring that all responses appear on a
new line. This is the default mode.
I [ Identify yourself ]
Issuing this command causes the chip to identify
itself, by printing the startup product ID string (this is
currently ‘ELM624 v3.0’). Software can use this to
determine exactly which integrated circuit it is talking
to, without resorting to resetting the entire IC.
L0 and L1
[ Linefeeds off (0) or on (1) ]
Many computer terminal programs expect a linefeed
character (hex 0A) to be sent after each carriage
return character (hex 0D). The sending of this
linefeed character is controlled by this option. Users
may find that for general use, leaving linefeeds on is
preferrable, but for some computer controlled
www.DataShaepept4liUc.actoimons, they may not require it (and could find
that it only serves to slow processing down). The
default setting is L1, linefeeds on.
MA [ Monitor All messages ]
Using this command places the ELM624 into a bus
monitoring mode, in which it displays all messages
as it sees them on the LANC bus. This continues
indefinitely until stopped by activity on the RS232
input. To stop the monitoring, one should send any
single character then wait for the ELM624 to respond
with a prompt character (‘>’). Waiting for the prompt
is necessary as time to respond is unpredictable,
and depends on what the IC was doing when
interrupted. If it were in the middle of printing a line, it
would first complete that line before sending the
prompt character, but if it were simply waiting for
input, it would return immediately. The character
which stops the monitoring will always be discarded,
and will not affect subsequent commands.
Q0 and Q1
[ Quiet mode off (0) or on (1) ]
This is a convenient means to stop the continuous
flow of status messages that occur while you are
experimenting. If quiet mode is selected, the chip will
function normally in all respects, except that the
sending of the LANC status messages will be
stopped. The default setting is Q0, quiet mode off.
RD [ send Raw Data ]
There may be times when one would like to see all
eight of the LANC words that are in a message
instead of just the four status bytes. There is not
enough time to send sixteen hexadecimal digits, a
carriage return and perhaps a linefeed character
while working with 60Hz systems, however. In order
to send this information, it must be kept in it’s un-
converted or ‘raw’ form.
In the raw data mode, the ELM624 performs no
translation of the received LANC data. It simply
leaves each byte as the raw value which was
received, and resends them to the connected PC
along with a single terminating carriage return
character. No linefeed is sent after the carriage
return, regardless of the AT L0/L1 setting. In the
Raw Data mode then, each eight byte LANC
message will always appear as a nine byte RS232
message.
This option will likely find limited use by many users
since many of the received values will represent
unprintable characters on a terminal screen, so will
require special capturing and processing for use. If it
is absolutely necessary to see what the value of the
four command words are, however, this is a means
to do so. Note that the values shown in the raw data
response are the result of actual bus reads, and not
simply a regurgitation of what is in the transmit
buffer. If there are bus conflicts or wiring problems,
the values may differ. By default, this mode is off.
R n [ Repeat commands n times ]
This sets the LANC command repeat value. Although
commands are only sent from the computer to the
ELM624 once, they must be sent to the Control L
device multiple times in order to be recognized. The
repeat value supplied (‘n’) can be any single hex
digit, which allows values in the range from 0 to 15
(hex F). Sending a 0 as the parameter (AT R0) is a
special case, which causes the command bytes to
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ELM624 pdf, datenblatt
ELM624
Power Control
Beginning with v3.0 of the ELM624, an output
pulse can be generated on the LANC output, simply by
issuing an AT SP command. The ‘pulse’ is actually an
active (low) signal that lasts for 150 milliseconds.
Many LANC devices respond to this pulse, some
by toggling the power on and off each time it is issued,
but most by waking up when they receive it. In order to
use this command, you would typically start the device
you wish to control, and either let it go to sleep by
itself, or issue a power off command (105E, 102A, or
something similar). When the device is in this ‘sleep
state’, it can often be ‘woken‘ simply by issuing a Send
Pulse command (AT SP). Note that not all devices can
be turned off by software commands, and not all will
wake up to this signal, but you may be fortunate and
yours may.
Monitoring from Powerup
The ELM624 IC can be put into a special
continuous monitoring mode at powerup, or during a
software reset (AT Z) without any input being required
from the user. This allows the IC to be used in
translator type projects such as ‘LANC logic probes’,
or simply inputs to computer based controllers.
If the RS232 Rx pin is found to be at an active
(high) level throughout the entire powerup sequence,
the IC will print the ID string (ELM624 v3.0), will set the
output mode to ‘Raw Data’, and will then immediately
go perform a monitor all command. This can be very
useful if all you need to do is to monitor the signals
being sent between other LANC devices. Note that in
the raw data mode, the ELM624 performs no
translation of the received LANC data. It simply leaves
each byte as the raw value which was received, and
resends them to the connected PC along with a single
terminating carriage return character. No linefeed is
sent after the carriage return, regardless of the AT
L0/L1 setting.
This monitoring mode will remain in effect until the
Rx input (pin 5) returns to a low level, no matter
whether there are sync signals or not, or even if there
are only sporadic sync signals. Once the Rx does go
low, the ELM624 will perform a ‘soft reset’, restarting
itself into the normal mode of operation. A software
and will be ready for your commands. The Example
Applications section shows an example of how you
might wire a ‘LANC logic probe’.
www.DaEtarSroheretM4Ue.csosmages
There are actually very few errors that the
ELM624 can report. There can be errors in the user
input, or there can be problems with the LANC signals:
NO SYNC
There is no recognizable synchronizing signal at the
ELM624’s LANC input. The IC has searched for
some time, attempting to detect a signal that it could
synchronize to, and failed. Check your connections,
and the power to the LANC device, then try again.
SYNC ERROR
A problem has occured while receiving one of the
eight LANC bytes. A synchronizing signal had been
detected, but either that was a false detection, or
something has now happened to the signal. As with
the NO SYNC condition, check your connections,
and the power to the LANC device, then try again.
?
This is the standard response for a misuderstood
command received on the RS232 bus. Usually it is
due to a typing mistake, but occasionally it can be
from problems with the connection to the computer.
ELM624DSD
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< http://www.elmelectronics.com/ >
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