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PCD5041

DECT burst mode controller

Philips Electronics 

Philips Semiconductors

DECT burst mode controller

Objective specification

PCD5041

are to be connected, the FS5 to FS12 signals have to be

generated externally. When using the framing signals

FS1 to FS4, no interface logic is required when using the

PCD5032 ADPCM CODEC.

A speech-slot control table is used to determine where to

store/fetch speech data for transmission and reception.

The hardware speech-interface is capable of addressing

the right speech buffer for the relevant speech slot, and will

maintain a counter carrying the offset to the correct

stored/fetched address.

6.4.2 MUTING

Due to various reasons the quality of the incoming speech

data may be degraded significantly. By muting the speech

data, these disturbances are not audible (or are less

audible) to the user. The PCD5041 performs two types of

muting:

• Fast muting

• Slow muting.

Fast muting, which is performed by the PCD5041

automatically, is nothing more than a repetition of the

previously received frame (80 speech samples) to the

ADPCM CODEC. It is issued if no Sync word was

detected. Slow muting is issued by the microcontroller,

after having detected a degradation of quality. A slow mute

is implemented as a continuous ‘0000’ nibble transmission

to the ADPCM CODEC, until slow mute is released.

6.4.3 LOCAL CALL

A local call option is implemented, in order to loopback

data from one CODEC to another CODEC, and vice versa,

see Fig.5.

handbook, halfpage

01

01

DO

speech buffer

pair

01

01

DI

speech slots

MBH710

6.5 RF interface

Most of the functions performed by the RF interface are

under control of the PCC. Specifically, the processing of

non-speech data and the programming of functions and

registers is done via the PCC.

6.5.1 SERIAL TRANSMITTER

The serial receiver processes the data, which comes from

the RF section, and which is already filtered by the

synchronization part. The data is latched, using the

recovered data clock.

The serial receiver will collect the complete A-field and

B-field and store it in the common data memory. Before the

A-field is received, the A-field start address is programmed

by the PCC. Upon reception of A-field nibbles, the address

is updated by the serial receiver. Meanwhile, the PCC will

program the B-field start address.

In Fig.6 the data flow in the serial receiver is shown. Note

that almost no decoding of messages is required. Only the

header of the A-field needs to be decoded to check if a

ciphered message is being received or transmitted, which

requires the ciphering to be switched on in the A-field also.

6.5.2 SERIAL RECEIVER

The serial transmitter performs the reverse of the receiver

functions. Several blocks used in the receiver are also

used in the transmitter. Amongst these are the

CRC-generators, the scrambler, and the address

registers. Figure 7 shows the serial transmitter structure.

By transmitting the X-CRC twice, the Z-field is transmitted.

The handling of the address registers is the same for the

transmitter. Transmission of the synchronization sequence

(S-field) is done using the same method as the A-field and

B-field. The S-field is stored in the common data memory

and will be fetched by the transmitter, just before

transmission.

Two additional functions are not shown in Fig.7:

• In the handset the data in the serial transmitter may be

advanced by a programmable number of bit periods.

This is done to compensate for the delay in the RF

section

• The transmitted data can be inverted (using a switch in

the PCD5041 mode register), in order to connect the

PCD5041 to VCOs requiring negative modulation.

Fig.5 Local call switching on speech interface.

1996 Oct 31

11

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