ELM624
Pin Descriptions
VDD (pin 1)
Rx (pin5)
This pin is the positive supply pin, and should
always be the most positive point in the circuit.
Internal circuitry connected to this pin is used to
provide power on reset of the microprocessor, so
an external reset signal is not required. Refer to
the Electrical Characteristics section for further
information.
The computer’s RS232 transmit signal is directly
connected to this pin through a single current
limiting resistor (typically about 47KW). Internal
signal inversion and Schmitt trigger waveshaping
provide the necessary signal conditioning.
Tx (pin 6)
The RS232 data output pin. Signal level is
compatible with most interface ICs, and drive is
sufficient to allow interfacing using only a single
PNP transistor if desired. See the Example
Application section for more details.
XT1 (pin 2) and XT2 (pin 3)
A 3.579545MHz NTSC television colourburst
crystal is connected between these two pins.
Crystal loading capacitors (typically 27pF) will
also normally be connected between each of the
pins and Vss.
LANC (pin 7)
This is the open drain Control L (LANC) interface
pin. An internal pullup resistor is provided for a
nominal drain load.
reset (pin 4)
This pin can be used to reset the circuit by
applying a momentary logic low level to it. If
unused, this pin should either be connected to
VDD, or left open (as an internal pullup resistor is
provided).
VSS (pin 8)
Circuit common is connected to this pin. This is
the most negative point in the circuit.
Ordering Information
These integrated circuits are available in either the 300 mil plastic DIP format, or in the 200 mil SOIC surface
mount type of package. To order, add the appropriate suffix to the part number:
300 mil Plastic DIP............................... ELM624P
200 mil SOIC..................................... ELM624SM
All rights reserved. Copyright ©1999 & 2000 Elm Electronics.
Every effort is made to verify the accuracy of information provided in this document, but no representation or warranty can be
given and no liability assumed by Elm Electronics with respect to the accuracy and/or use of any products or information
described in this document. Elm Electronics will not be responsible for any patent infringements arising from the use of these
products or information, and does not authorize or warrant the use of any Elm Electronics product in life support devices and/or
systems. Elm Electronics reserves the right to make changes to the device(s) described in this document in order to improve
reliability, function, or design.
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