1999 Aug 26

8

Philips Semiconductors

Product specification

Self Tuned Radio (STR)

TEA5757; TEA5759

Description of the bus

The TEA5757; TEA5759 radio has a bus which consists of

three wires, as shown in Table 1.

Table 1

Bus signals

These three signals, together with the mono/stereo pin

(MO/ST; pin 24), communicate with the microcontroller.

The mono/stereo indicator has two functions, which are

controlled by the BUS-CLOCK, as shown in Table 2.

Table 2

Bus-clock functions

The TEA5757; TEA5759 has a 25-bit shift register;

see Table 3 for an explanation of the shift register bits.

If in search mode no transmitter can be found, all

frequency bits of the shift register are set to logic 0.

The bus protocol is depicted in Figs 3 and 4.

SIGNAL

DESCRIPTION

PIN

BUS-CLOCK

software driven clock input

27

DATA

data input/output

28

WRITE-ENABLE write/read input

29

BUS-CLOCK

MO/ST (PIN 24)

RESULT

LOW

LOW

stereo

LOW

HIGH

mono

HIGH

LOW

tuned

HIGH

HIGH

not tuned

Table 3

Explanation of the shift register bits

Note

1. The output pins 30 and 31 can drive currents up to 5 mA; bits P0.19 and P1.18 control the output voltage of the

control pins P0 (pin 30) and P1 (pin 31):

a) Bit P0.19 LOW sets P0 (pin 30) to LOW.

b) Bit P0.19 HIGH sets P0 (pin 30) to HIGH.

c) Bit P1.18 LOW sets P1 (pin 31) to LOW.

d) Bit P1.18 HIGH sets P1 (pin 31) to HIGH.

BIT

DESCRIPTION

LOGIC

STATE

RESULT

S.24 (MSB)

search start/end

0

after a search when a station is found or after a preset

1

during the search action

D.23

search up/down

0

indicates if the radio has to search down

1

indicates if the radio has to search up

M.22

mono/stereo

0

stereo is allowed

1

mono is required (radio switched to forced mono)

B0.21

band

see Table 4 selects FM/MW/LW/SW band

B1.20

P0.19

port

note 1

user programmable bits which e.g. can be used as band

switch driver

P1.18

S0.17

search-level of station

see Table 5 determines the locking field strength during an

automatic search, automatic store or manual search

S1.16

15

dummy

−

buffer

F.14 to F.0 (LSB)

frequency

−

determine the tuning frequency of the radio; see Table 6

for the bit values