ELM303
Functional Block Diagram
The operation of the ELM303 can best be
described through the following block diagram. All
of the main functions are shown, while initialization,
timekeeping, etc. are implied. The power on and off
delays are internally set, and are not adjustable.
PowerUp
Loop
wait 1 minute
wait for timeout
or I=’000’
Note that on powerup, and after responding to
a ‘000’ interval code, the circuit always initiates a
record cycle after one minute. This allows the
operator to verify that the system is operating
properly.
Save the state
of all pins
no
Control L
bus active
?
Pulse Power
for 200msec
yes
wait 10 sec
send 0x1833 to
the camcorder
if D0=0, wait 1s
else wait 10s
yes
Is
I=’000’
?
no
yes
Was
I=’000’
?
send 0x1833 to
the camcorder
no
send 0x1833 to
the camcorder
wait 5 sec
Pulse Power
for 200msec
wait 5 sec
Go to PowerUp
Pulse Power
for 200msec
Go to Loop
ELM303DSA
Elm Electronics – Circuits for the Hobbyist
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