1998 May 11
7
Philips Semiconductors
Product specification
8-bit microcontroller with DTMF
generator and 128 bytes EEPROM
PCD3359A
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, or the melody function is
used, the TONE output is in 3-state mode.
6.1
Frequency generator derivative registers
6.1.1
H
IGH AND
L
OW
G
ROUP
F
REQUENCY
R
EGISTERS
Table 3 gives the addresses, symbols and access types of the High Group Frequency (HGF) and Low Group Frequency
(LGF) Registers.
Table 3
Hexadecimal addresses, symbols, access types and bit symbols of the frequency registers
6.1.2
M
ELODY AND
P
ORT
I
NTERRUPT
C
ONTROL
R
EGISTER
(MDYCON)
The Melody and Port Interrupt Control Register has two functions: bit 0 defines the behaviour of the melody output; bits
4 to 7 individually enable/disable specific pairs of Port 0 interrupts. MDYCON is a R/W register.
Table 4
Melody and Port Interrupt Control Register (address 13H)
Table 5
Description of MDYCON bits
REGISTER
ADDRESS
REGISTER
SYMBOL
ACCESS
TYPE
BIT SYMBOLS
7
6
5
4
3
2
1
0
11H
12H
HGF
LGF
W
W
H7
L7
H6
L6
H5
L5
H4
L4
H3
L3
H2
L2
H1
L1
H0
L0
7
6
5
4
3
2
1
0
EPI3
EPI2
EPI1
EPI0
0
0
0
EMO
BIT
SYMBOL
DESCRIPTION
7 to 4
EPI3 to EPI0
Enable Port 0 interrupts.
Bits 7 to 4 individually enable/disable specific pairs of Port 0
interrupts; see Table 6 and Section 8.2 for details.
These bits are set to a logic 0.
EMO
Enable Melody Output.
If bit EMO = 0, then P1.7/MDY is a standard port line and the
TONE output is enabled. If bit EMO = 1, then P1.7/MDY is the melody output and the
TONE output is disabled (3-state). 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.
3 to 1
0