ICM7115

Rev. 2.5

ICmic reserves the right to change the specifications without prior notice

5

present, the typical AC impedance is 1000 .

Refer to Figure 2 for the equivalent test circuit.

typically sets the AC impedance

to 600 . Please note that the overall system

AC impedance also depends on the whole

system circuit.

DTMF Signal Level

DTMF signal level can be selected by setting

MFL0 pin as follow:

MFL0

DTMF level

0

Low, typical -8/-10dB

1

High, typical -6/-8dB

DIALING FUNCTIONS

Keypad arrangement is as shown in the typical

application circuit in Appendix A. Dialing

modes are selectable using the pull-up/pull-

down resistors connected to the row inputs.

As soon as the phone goes off-hook (i.e when

HS_DPB pin goes HIGH), voltage levels on

keypad row inputs (R1 thru R4) are first

scanned to determine the operating mode as

follow:

Pin

Function

Level – Mode

R1

Dialing Mode

0 – MF mode

1 – Pulse mode

R2

Pulse Period

0 – 10 PPS

1 – 20 PPS

R3

Make/Break

Ratio

0 – 40/60

1 – 33/67

R4

DTMF option

0 – 82ms/82ms

1 – 82ms/160ms

Valid Keys

ICM7115 has a total of 16 valid keys. It scans

the keys by asserting known state on pins R1,

R2, R3, and R4 in sequence, and check which

column (pins C1B, C2B, C3B, C4B) is shorted

to which row. The following specify the

combinations:

C1B

C2B

C3B

C4B

R1

1

2

3

Vol_up

R2

4

5

6

Vol_Down

R3

7

8

9

Flash

R4

*

0

#

LNR

DTMF Tones

The DTMF tone generator creates 12 tones in

compliance

with

CCITT

Recommendation.

There are two group of frequencies of DTMF

tones. The low group depends on the key’s

row, while the high group depends on the

key’s column as illustrated in the following

table:

C1B

C2B

C3B

Low

Freq

R1

1

2

3

697 Hz

R2

4

5

6

770 Hz

R3

7

8

9

852 Hz

R4

*

0

#

941 Hz

Last Number Redial (LNR)

The last Number Redial (LNR) is a facility of

ICM7115 to allow resignalling of the last

manually dialled number without keying in all

digits again. The LNR is repeatable after each

off-hook.

A manually entered number is stored in

internal 32-digit RAM. VDD shall not fall below

1.0V during on-hook state to properly retain

the data in the memory.

Flash

ICM7115

asserts

line

break

(pulls

down

HS_DPB pin) when Flash key is depressed. The

flash duration depends on the input levels of

FOPT0 pin as follow:

FOPT0

Flash Duration

0

300 ms

1

600 ms

Vol_Up

When Vol_Up key is depressed ICM7115

increases the receive gain by 13.5dB in three

steps (from default level).

Vol_Down

When Vol_Down key is depressed ICM7115

decreases the receive gain by -10.5dB in four

steps (from default level).