© 2002 Microchip Technology Inc.

DS21475B-page 5

TC818A

2.0

PIN DESCRIPTIONS

Thedescriptionsof the pins arelistedinTable2-1.

TABLE 2-1:

PIN FUNCTION TABLE

Pin Number

(64-Pin PQFP)

Symbol

Description

1

NC

No connection.

2OHM

Logic Input. “0” (Digital Ground) for resistance measurement.

320mA

Logic Input. “0” (Digital Ground) for 20mA full scale current measurement.

4

BUZ

Buzzer. Audio frequency, 4kHz, output for continuity indication during resistance

measurement. A noncontinuous 4kHz signal is output to indicate an input over range

during voltage or current measurements.

5

XTAL1

32.768kHz Crystal Connection.

6

XTAL2

32.768kHz Crystal Connection.

temperature variation of LCD crystal threshold voltage.

8

BP1

LCD Backplane #1.

9

BP2

LCD Backplane #2.

10

BP3

LCD Backplane #3.

11

LO

Ω/A

LCD Annunciator segment drive for low ohms resistance measurement and current

measurement.

12

Ω/V

LCD Annunciator segment drive for resistance measurement and voltage measurement.

13

k/m/HOLD

LCD Annunciator segment drive for k (“kilo-Ohms”), m (“milliamps” and “millivolts”) and

HOLD mode.

14

BCP0

(One’s digit)

LCD segment drive for “b,” “c” segments and decimal point of least significant digit (LSD).

15

AGD0

LCD segment drive for “a,” “g,” “d” segments of LSD.

16

FE0

LCD segment drive for “f” and “e” segments of LSD.

17

NC

No connection.

18

BCP1

LCD segment drive for “b,” “c” segments and decimal point of 2nd LSD.

19

AGD1

LCD segment drive for “a,” “g,” “d” segments of 2nd LSD.

20

FE1

LCD segment drive for “f” and “e” segments of 2nd LSD.

21

BCP2

LCD segment drive for “b,” “c” segments and decimal point of 3rd LSD

(hundred’s digit).

22

AGD2

LCD segment drive for “a,” “g,” “d” segments of 3rd LSD.

23

FE2

LCD segment drive for “f,” “e” segments of 3rd LSD.

24

BCP3

LCD segment drive for “b,” “c” segments and decimal point of MSD,

(thousand’s digit).

25

AC/-/AUTO

LCD annunciator segment drive for AC measurements, polarity, and auto-range operation.

26

-MEM/BATT LCD annunciator segment drive for AC for low battery indication and memory (relative

measurement).

27

ANNUNC

Square wave output at the backplane frequency, synchronized to BP1. ANNUNC can be

used to control display annunciators. Connecting an LCD segment to ANNUNC turns it on;

connecting it to its backplane turns it off.

28

Positive battery supply connection.

29

COM

30

DEINT

De-integrate output.

31

Ratiometric (resistance measurement) reference low voltage.

32

33

34

REFHI

Reference voltage for voltage and current measurement. Nominally 163.85mV.

35

ΩR1

Standard resistor connection for 200

Ω full scale.

36

ΩR2

Standard resistor connection for 2000

Ω full scale.