1997 Apr 16

7

Philips Semiconductors

Product specification

8-bit microcontrollers with DTMF generator,

8 kbytes OTP and 128 bytes EEPROM

PCD3755A; PCD3755E;

PCD3755F

6

FREQUENCY GENERATOR

A versatile frequency generator section is provided (see

Fig.4). For normal operation, use a 3.58 MHz quartz

crystal or PXE resonator. The frequency generator

includes precision circuitry for dual tone multifrequency

(DTMF) signals, which is typically used for tone dialling

telephone sets.

Their frequencies are provided in purely sinusoidal form on

the TONE output or as square waves on the P1.7/MDY

output.

The TONE output can alternatively issue twelve modem

frequencies for data rates between 300 and 1200 bits/s.

In addition to DTMF and modem frequencies, two octaves

of musical scale in steps of semitones are available.

In case no tones are generated the TONE output is in

3-state mode.

6.1

Frequency generator derivative registers

6.1.1

Table 3 gives the addresses, mnemonics and access types of the High Group Frequency (HGF) and Low Group

Frequency (LGF) registers.

Table 3

Hexadecimal addresses, mnemonics, access types and bit mnemonics of the frequency registers

6.1.2

MDYCON is a R/W register.

Table 4

Melody Control Register (address 13H)

Table 5

Description of MDYCON bits

REGISTER

ADDRESS

REGISTER

MNEMONIC

ACCESS

TYPE

BIT MNEMONICS

7

6

5

4

3

2

1

0

11H

HGF

W

H7H6H5H4H3H2H1H0

12H

LGF

W

L7L6L5L4L3L2L1L0

7

6

5

4

3

2

1

0

0000000

EMO

BIT

MNEMONIC

DESCRIPTION

7to1

−

These bits are set to a logic 0.

0

EMO

Enable Melody Output. If bit EMO = 0, then P1.7/MDY is a standard port line.

If bit EMO = 1, then P1.7/MDY is the melody output. EMO = 1 does not inhibit the port

instructions for P1.7/MDY. Therefore the state of both port line and flip-flop may be read

in and the port flip-flop may be written by port instructions. However, the port flip-flop of

P1.7/MDY must remain set to avoid conflicts between melody and port outputs.

When the HGF contents are zero while EMO = 1, P1.7/MDY is in the logic HIGH state.