ELM415

Elm Electronics – Circuits for the Hobbyist

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Pin Descriptions

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............................... ELM415P

200 mil SOIC..................................... ELM415SM

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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.

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.

Up/Down (pin 2)

This is the count direction output, which changes

state depending on which pushbutton is being

pressed. If it is the Up pushbutton, this output will be

at a high level, while a Down results in it being at a

low level. The output remains at a level until the

alternate pushbutton is pressed. When it does

change, it does so approximately 1 msec prior to an

active pulse appearing on Count.

Count (pin 3)

This output provides a pulsing signal in response to

one

of

the

two

pushbuttons

being

pressed.

Simultaneous pressing of both switches is detected

and results in no output. The width of the output

pulse is fixed at approximately 1 msec, but the

polarity can be changed depending on the level at

the Invert input. This output is used to ‘clock’ the

controlled counter circuit.

Invert (pin 4)

This input controls the quiescent level at pin 3 (the

Count output). If low, the level at pin 3 will also

normally be low, pulsing momentarily to a high level

when a button is pressed. Setting this pin high

causes pin 3 to rest at a high level, with the output

pulses momentarily going low.

Repeat (pin 5)

This input controls the circuit response should one of

the pushbuttons be continuously pressed. If this pin

is at a low level, there will only be a single Count

output generated, no matter how long the button

stays pressed. If this pin is at a high level, a single

pulse is output, then after a short delay, a continuous

stream of pulses are generated for as long as the

button is held.

UpSw (pin 6) and DownSw (pin 7)

The pushbuttons are connected to these pins.

Internal pullup resistors are provided to bias the

input when no button is pressed, simplifying the

circuitry required. These are standard CMOS inputs,

so the use of external delay components (capacitors,

etc.) is not recommended.

Circuit common is connected to this pin. This is the

most negative point in the circuit.

ELM415DSA