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No. 5157-8/16

LC72336, 72338

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Pin No.

Symbol

I/O

I/O type

Function

72

71

SNS

LCTR

I

I

CMOS input

CMOS amplifier

input

Shared-function voltage sensing input and general-purpose input port

The input threshold voltage is set lower than that of other inputs.

• When used as a voltage sensing pin:

This pin is used to recognize power failures on recovery from backup (clock stop) mode.

An internal sensing flip-flop is used for this determination. The TUL instruction (b2) can

be used to test the sense flip-flop.

• When used as a general-purpose input port:

Use the TUL instruction (b3) to test this pin when it is used as a general-purpose input

port.

Unlike other input ports, input is not disabled during clock stop mode or a power-on reset.

Thus applications must take through currents into consideration if this pin is used as a

general-purpose input port.

Shared-function universal counter (frequency or period measurement) and general-

purpose input port

The IOS instruction (Pn = 3, b3) is used to switch this pin between its universal counter

and general-purpose input port functions.

• When used for frequency measurement:

Select the universal counter function with an IOS instruction (Pn = 3, b3 = 0).

Set LCTR frequency measurement mode with a UCS instruction (b3 = 0, b2 = 1). After

selecting the measurement time, start the counter with a UCC instruction.

The CNTEND flag will be set when the count completes.

Since this circuit operates as an AC amplifier in this mode, the input must be capacitor

coupled.

• When used for period measurement:

With the universal counter function selected, set period measurement mode with a UCS

instruction (b3 = 1, b2 = 0). After selecting the measurement time, start the counter with

a UCC instruction.

The CNTEND flag will be set when the count completes.

Since the bias feedback resistor is switched off in this mode, the input must be DC

coupled.

• When used as a general-purpose input port:

Specify the general-purpose input port function with an IOS instruction (Pn = 3, b3 = 1).

Use the INR (b1) internal register (address 0EH) input instruction to read in the input

data.

Input is disabled in clock stop mode. (The input pin is pulled down.)

The universal counter function is selected after a power-on reset. (HCTR frequency

measurement mode.)