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ELM633 데이터시트 PDF




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부품번호 ELM633 기능
기능 19200bps miniLIN Monitor
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ELM633 데이터시트, 핀배열, 회로
ELM633
19200bps miniLIN Monitor
Description
LIN or ‘Local Interconnect Network’ is a low cost
and relatively simple networking system that is used
predominantly in the automotive world. Recently, it
has been gaining in popularity with proposals to use
it in major appliances as well. For more information,
visit the LIN web site (http://www.lin-subbus.de/).
The ELM633 is a monitoring device designed
for troubleshooting LIN bus systems. It is capable of
continually monitoring a LIN network, translating the
LIN messages to standard ASCII characters, and re-
transmitting them to an RS232 system (personal
computer or PDA) for display and possibly for
analysis. The synchronizing, data formatting, and
checksum calculations are all done for you by the
ELM633.
The LIN specification has recently been updated
to revision 2.0, incorporating several improvements.
The ELM633 has been updated to be compatible
with this new specification, as well as the previous
ones.
Applications
• LIN logic probes
www.DataSheeDt4iaUg.cnoomstic PC interfaces
• Instruction triggered (breakpoint) devices
• Educational or training devices
Features
• Low power CMOS design
• Crystal controlled for accuracy
• Standard ASCII character output
• Special power-on monitor mode
• Permanently set to a 19200bps LIN rate
• High speed (57600 baud) RS232 interface
• Works with LIN1.x and LIN2.0
Connection Diagram
PDIP and SOIC
(top view)
VDD 1
XT1 2
XT2 3
Rxmode 4
8 VSS
7 LIN
6 RS232Tx
5 RS232Rx
Block Diagram
RS232Tx 6
RS232Rx 5
Rxmode 4
RS232
Interface
3.58MHz
XT1 2
3 XT2
Timing
Formatting
and
Control
LIN
Interface
7 LIN
ELM633DSB
Elm Electronics – Circuits for the Hobbyist
< http://www.elmelectronics.com/ >
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ELM633 pdf, 반도체, 판매, 대치품
ELM633
Communicating with the ELM633
The ELM633 relies on a standard RS232 serial
connection to communicate with the user. The data
rate is not adjustable and is set at 57600 baud, with 8
data bits, no parity bit, 1 stop bit, and no handshaking
(often referred to as 57600 8N1). All responses from
the IC are terminated with a single carriage return
character and, optionally, a linefeed character. Make
sure your software is configured properly for this
connection (and the linefeed mode that you have
chosen). No special software is required to ‘talk’ to the
IC – a standard terminal program is all that is needed.
Once it has been properly connected and
powered, the ELM633 will send the message:
ELM633 v2.0
>
In addition to identifying the version of this IC,
receiving this string is a good way to confirm that the
computer connections and terminal software settings
are correct. The ‘>’ character displayed above is the
ELM633’s prompt character, which shows that the
device is in its idle state, ready to receive characters
on the RS232 port.
All messages that are sent to the ELM633 must
begin with the character ‘A’ followed by the character
‘T’, and must be terminated with a carriage return
character. No action is taken – commands are not
checked for errors, nor are they acted upon – until this
www.DatatSehrmeeitn4Uat.cinogm carriage return is received. The one
exception is when a command is interrupted for some
reason, and no carriage return appears. In this case,
an internal timer will automatically abort the incomplete
message after about 15 seconds, and the ELM633 will
print a single question mark to show that the input was
not understood (and was not acted upon).
Messages that are not understood by the ELM633
(syntax errors) will always be signalled by this same
single question mark (‘?’). When this occurs, it is
usually due to a spelling mistake, so you often only
need to repeat the input, typing more carefully.
Occasionally, errors occur if the ELM633 is busy
processing LIN messages when an RS232 command
message begins. In these cases, the first character of
the RS232 command message will always be missed
by the IC, so the remaining characters will appear to
be incorrect. You should always interrupt the
monitoring process with a single character (it doesn’t
matter which one, as it will be ignored), then wait for
the prompt character (“>”) to appear before sending
any more. This ensures that the ELM633 is ready to
receive commands.
For convenience, the ELM633 has been designed
to ignore spaces and control characters in the input, so
if you prefer to add spaces, tabs, etc., to improve
readability, then go ahead. Also, the ELM633 is not
case-sensitive, so ‘ATZ’ is equivalent to ‘atz’ and to
‘AtZ’, which may be helpful for some people.
AT Commands
The ELM633 is controlled with short commands
that all begin with the two characters ‘AT’ (which is
short for ATtention). These two characters serve no
purpose other than to help add validity to the
characters that follow. Modem manufacturers have
used this same technique for years, and it has become
customary to refer to commands that begin with these
characters as ‘AT Commands’.
The ELM633 accepts several different AT
commands, but only one at a time (it cannot process
multiple commands on one line, as most modems
can). Each is executed only upon receipt of the
terminating carriage return character. Several
commands do not have a visible response (AT D for
example), so completion of those commands will be
acknowledged by the printing of the characters ‘OK’.
Monitoring of the LIN bus can generally begin
without requiring the use of any AT commands, as the
factory default settings should be appropriate for most
situations. Occasionally, however, the user may wish
to customize settings, such as turning the character
echo off, and in these cases, AT commands must be
used.
To perform the desired AT command, simply send
the characters AT followed by the appropriate
characters from the following list. For example, to turn
character echoing off, simply send AT E0 followed by
a return character. To turn it back on, send AT E1.
The following is a summary of the commands that
are recognized by the current version of the ELM633.
ELM633DSB
Elm Electronics – Circuits for the Hobbyist
< http://www.elmelectronics.com/ >
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ELM633 전자부품, 판매, 대치품
ELM633
Monitoring the LIN Bus
Data bytes that appear on the LIN bus can
assume values from 0 to 255. These cannot be
displayed using a PC terminal program, however,
since many of these values are not printable
characters. In order to make them readable, the
ELM633 re-formats every byte as a pair of
hexadecimal digits, using standard ASCII characters.
A typical request made of the ELM633 would appear
as:
>AT MA
49: 6C 8F 04
The AT MA is the user’s request to ‘monitor all’,
while the 49: 6C 8F 04 is what the ELM633 found on
the LIN bus. Note that the initial Synch Byte is always
received, but is never displayed (it is always 55).
The identifier byte (49 in this example) always
appears first, and is separated from the data bytes by
a colon character (“:”), while the pairs of hexadecimal
digits following represent the data bytes that were
received. The final pair of digits on each line is the
checksum byte (04 in this case).
Should the checksum byte not match the value
calculated internally by the ELM633, the error will be
flagged by printing a single question mark at the end of
the line. For an example, if the slave driver in the
above case was weak, allowing an extra ‘1’ to appear
in the first data byte of this example, the output might
typically look like:
www.DataShee>t4AUT.cMomA
49: 6C 8F 04
49: 7C 8F 04?
The question mark at the end of the second
response line alerts you to the fact that an error is
present, but the position of the error cannot be
determined from this information – you will only be
able to say that it is somewhere in the response.
Another type of error that could occur is when a slave
fails to respond to the master. In this case, you would
typically see only the identifier, followed by a single
question mark:
>AT MA
49:?
The question mark gets printed in this case
because 49 is not a valid checksum byte (all bytes
must add up to FF).
Often, this would be followed by a timeout so the
output could appear as:
>AT MA
49:
[T]
As you experiment, you will likely find that
timeouts are a very common occurence. They simply
mean that there has been no activity for some time,
often due to the system going into a low-power sleep
mode. Error messages are described further in the
next section.
This data is typical of what might be experienced
in many systems. The current version of the LIN
standard (2.0) allows for the possibility of an arbitrary
number of data bytes however, so while the ELM633
has no limitations on what it can display, the user
should be prepared for this possibility. This could
involve simply allocating enough buffer space,
processing the data faster than it arrives, or by simply
ignoring lines that are longer than a predetermined
length.
The ELM633 also supports one other type of
monitoring command, which is useful when you know
the specific responses that you wish to view. It is the
AT MR command, which requests that only specific
responses to ID bytes be displayed, while ignoring all
others. For instance, a ‘monitor all’ command might
have resulted in:
>AT MA
D3: C0 00 3F
49: 6C 8F 04
92: D4 00 2B
D3: C0 00 3F
.
.
.
Only a portion of the data stream is shown, as it
can typically be quite lengthy. However, if the user was
only interested in responses that began with 92 for
instance, they need only issue an AT MR 92 command
to filter the information for them. The above would
have looked like:
>AT MR 92
92: D4 00 2B
This command is often helpful when trying to
diagnose a particular problem.
ELM633DSB
Elm Electronics – Circuits for the Hobbyist
< http://www.elmelectronics.com/ >
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