1997 Apr 16

4

Philips Semiconductors

Product specification

PCF1172C

Fig.2 Segment designation of LCD.

MSA989

B1

C1

A2

G2

D2

F2

E2

B2

C2

P1 (P3)

P2 (P4)

A3

G3

D3

F3

E3

B3

C3

A4

G4

D4

F4

E4

B4

C4

AM

PM

Fig.3 Display mode (12-hour with AM/PM annunciator).

TIME

MSA990

AM

OPERATIONAL INPUTS

Operational inputs S1, S2 and S3 have an internal pull-up

resistor to facilitate use of external single-pole,

single-throw switches. A specific debounce circuit is

integrated as protection against contact debounce and

parasitic voltages.

In the description below, an arrangement as shown in

Fig.5 is assumed and S1, S2 and S3 refer to the external

switches rather than the corresponding inputs.

Set hours, switch S1

Closure of S1 increments the hours according to the

correction mode selected by S6 (see Chapter “Input

options”).

Set minutes/reset seconds, switch S2

When S2 is closed, the minute setting is corrected

according to the correction mode determined by S6 (see

Chapter “Input options”).

The seconds counter is reset to zero each time S2 is

closed, and begins running each time S2 is opened.

Segment test/reset, switches S1 and S2

If S1 and S2 are closed simultaneously all LCD segments

are switched on. When the switches are released, the

clock starts at 1 : 00.