ELM329L
Pin Descriptions
MCLR (pin 1)
or disabled with the AT M1 and AT M0 commands.
A momentary (>2µsec) logic low applied to this input
will reset the ELM329. If unused, this pin should be
connected to a logic high (VDD) level.
Filter Cap (pin 6)
The ELM329L requires that a 10µF filter capacitor be
connected between pin 6 and VSS. The capacitor
should be a low ESR (<5W) ceramic or tantalum
type.
Vmeasure (pin 2)
This analog input is used to measure a 0 to VDD volt
signal that is applied to it. The value measured is
scaled by a factor of 5.7 if VDD is >4V, and by a
factor of 11 if VDD is <4V. The scaling is appropriate
for use with 47KW/10KW and 47KW/4.7KW resistor
dividers, respectively. The measured voltage is
displayed using the AT RV command.
The ELM329 uses pin 6 for setting the initial baud
rate after power on. Since this option is not available
with the ELM329L, it defaults to an initial baud rate
of 38400 bps. If you require 9600 bps, you must set
PP 0C to 00.
Care must be taken to prevent the voltage from
going outside of the supply levels of the ELM329, or
damage may occur. If it is not used, this pin should
be tied to either VDD or VSS.
LFmode (pin 7)
This input is used to select the default linefeed mode
to be used after a power-up or system reset. If it is at
a high level, then by default messages sent by the
ELM329 will be terminated with both a carriage
return and a linefeed character. If it is at a low level,
lines will be terminated by a carriage return only.
This behaviour can always be modified by issuing an
AT L1 or AT L0 command.
Active LED (pin 3)
This output pin is normally at a high level, and is
driven to a low level when the ELM329 has
determined that it has found a valid (active) protocol.
The output is suitable for directly driving efficient
LEDs through a current limiting resistor, or for
interfacing to other logic circuits. If unused, this pin
may be left open-circuited.
VSS (pin 8)
Circuit common must be connected to this pin.
Note that the behaviour of this pin when the ELM329
is in the low power mode may be modified by the
logic level at pin 11, or with PP 0F, bit 4. For the
ELM329L, the total current into or from pin 3 must
not exceed 2 mA.
XT1 (pin 9) and XT2 (pin 10)
A 4.000 MHz oscillator crystal is connected between
these two pins. Loading capacitors as required by
the crystal (typically 27pF each) will also need to be
connected from each of these pins to circuit common
(Vss).
Control (pin 4)
When laying out a printed circuit board, you may
wish to consider placing a guard ring around the
oscillator crystal, pins, and capacitors, to provide a
little isolation between them and the other signals
(particularly the pin 11 CAN input).
The level at this output may be directly controlled
through AT commands. After any reset (powerup,
AT Z, etc.), the output reverts to a low level.
Pin 4 may also be used to provide an output signal
that follows the internal CAN monitor output, by
setting bit 0 of PP 0F to 1. For the ELM329L, the
total current into or from pin 4 must not exceed 2
mA.
Note that this device has not been configured for
operation with an external oscillator, and it expects a
crystal to be connected to these pins. Use of an
external clock source is not recommended. Also,
note that this oscillator is turned off when in the low
power or ‘standby’ mode of operation.
Memory (pin 5)
This input controls the default state of the memory
option. If this pin is at a high level during power-up or
reset, the memory function will be enabled by
default. If it is at a low level, then the default will be
to have it disabled. Memory can always be enabled
CAN Monitor (pin 11)
This input serves two functions. If a CAN signal is
detected at this pin, the ELM329 assumes that you
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ELM329L DSA
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