3

Application Information

V

DD

V

DD

V

SS

V

SS

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

FX623P

XTAL/CLOCK

P URS

DATA CHANGE

SIGNAL IN

COMPOSITE SIGNAL IN

A HEX Code

Output representing

the decoded tone

frequency

See Table 1

DATA OUTPUTS

Q3

Q0

Q1

Q2

V

SS

XTAL

HOLD

IRQ

CS

Fig.2 Recommended External Components

Band Edges (Hz)

Nominal

Hex

Output Code

Lower

Upper

Centre

Character Q3 Q2 Q1 Q0

Edge

Edge

Freq.

0

0000

364

386

375

1

0001

488

520

500

2

0010

520

580

550

3

0011

580

618

600

4

0100

386

412

400

5

0101

412

436

425

6

0110

436

463

450

7

0111

463

487

475

8

1000

900

1008

950

9

1001

1273

1325

1300

A

1010

1350

1455

1400

B

1011

1750

1855

1800

C

1100

2062

2140

2100

D

1101

frequency not guaranteed

E

1110

frequency not guaranteed

F

1111

Table 1 Tone Decode Frequencies

Timing Information

With CS Low - Figure 3.

After initial power-up and the Hold input inactive

(High), as frequencies are input, with the Data Change

output as an active (High) indicator, the data is

presented at the Data Outputs.

If/when the Hold input is placed active (Low), the

data at the Data Outputs is frozen and the Data

Change output held High at its next active excursion -

until the Hold input is returned High.

With the Hold input held High - Figure 4.

As frequencies are input a correct decode will

produce an active (Low) interrupt level.

This interrupt (IRQ) is serviced and reset by an

active (Low) CS input.

Note the ‘valid data’ period at the Data Outputs.

Component

Value

R

1

1.0M

Ω

R

2

1.0M

Ω

C

1

47.0nF

C

2

4.7nF

C

3

33.0pF

C

4

33.0pF

C

5

1.0µF

X

1

3.579545MHz

Tolerances R = ±10%

C = ±20%