TLF6681 – 3

FIGURE 2 Crystal Oscillator

DAYS COUNTER

There are two Days counters

a) units of days

b) tens of days

The Days counters will count up to 28 29 30 or 31 days

depending on the state of the Months counters and the

Years Status Register Days counters have parallel load and

read multiplex capabilities

MONTHS COUNTERS

There are two Months counters

a) units of months

b) tens of months

The Months counters have parallel load and read multiplex

capabilities

YEARS STATUS REGISTER

The Years Status register is a shift register of 4 bits It will be

shifted every year on December 31st The status register

must be set in accordance with Table III No readout capa-

bility is provided

CHIP SELECT (CS)

An external chip select is provided The chip enable is ac-

tive low

COUNTER AND REGISTER SELECTION

Table I shows the coding on the address lines AD0 – AD3

which select the registers in the circuit to be either parallel

loaded or read on to the output bus

TLF6681 – 4

FIGURE 3 Test Mode Organization

STARTSTOP (RESET) LATCH

A logic ‘‘1’’ on DB0 at chip address 14 (E) will start the clock

running a logic ‘‘0’’ will stop the clock This function allows

the loading of time data into the clock and its precise start-

ing The clock starts at 01 seconds

TEST MODE

This mode is incorporated to facilitate production testing of

the circuit In this mode the 32768 Hz clock is fed forward

as shown in

Figure 3 For normal operation the circuit must

be set to the non-test mode as part of the system initializa-

tion This is accomplished by writing a logic ‘‘0’’ to DB3 at

AD0

TABLE I Address Decoding for Internal Registers

Selected

Counter

Address Bits

Mode

AD3 AD2 AD1 AD0

0 Test Only

0

0

0

0

Write Only

1 Tenths of Secs

0

0

0

1

Read Only

2 Units of Secs

0

0

1

0

Read Only

3 Tens of Secs

0

0

1

1

Read Only

4 Units of Mins

0

1

0

0

Read or Write

5 Tens of Mins

0

1

0

1

Read or Write

6 Units of Hours

0

1

1

0

Read or Write

7 Tens of Hours

0

1

1

1

Read or Write

8 Units of Days

1

0

0

0

Read or Write

9 Tens of Days

1

0

0

1

Read or Write

10 Day of Week

1

0

1

0

Read or Write

11 Units of Months

1

0

1

1

Read or Write

12 Tens of Months

1

1

0

0

Read or Write

13 Years

1

1

0

1

Write Only

14 StopStart

1

1

1

0

Write Only

15 Interrupt

1

1

1

1

Read or Write

4