PCF5001 datasheet(13/44 Pages) PHILIPS

13 / 44 page

1997 Mar 04

Philips Semiconductors

Product speciﬁcation

POCSAG Paging Decoder

PCF5001

This is carried out for the duration of 3 batches in

power-on mode or 1 batch (=preamble duration) in

preamble receive mode. Error correction algorithms are

applied to the data before it is compared with preamble

and synchronization codeword patterns.

The synchronization process is terminated and thus

data receive mode is entered as soon as synchronization

codewords are seen at the beginning of each batch.

The decoder handles loss of synchronization in three

steps:

1. If the decoder fails to detect the synchronization

pattern at the beginning of the current batch it

continues data reception as normal. This data fail

mode is signalled in the message output when an

address codeword was received, as shown in Table 4.

2. If also at the beginning of the next batch no

synchronization codeword can be detected, the

algorithm assumes a small bit shift in the

fade recovery mode and performs more

synchronization codeword checks around the

expected position for the following 15 batches. Call

reception is suspended.

3. If it fails to re-synchronize in the ‘fade recovery’ mode,

the carrier off mode is selected, in which the decoder

attempts to regain synchronization by bit-wise shifting

its synchronization scan window. Using this technique

re-synchronization is obtained within a continuous

data stream of at least 18 batches without preamble

detection.

In ‘data receive’ mode, the input data stream is sampled at

the synchronization codeword position and the

programmed frame positions. The received codewords are

error corrected and then, if address codewords, compared

with the stored user addresses related to that frame.

On detection of a valid call, the decoder performs the

following three operations:

1. Set a store for call alert cadence generation according

to the combination of the function bits in the accepted

address codeword. The call alert cadence will not be

generated before the call has been terminated.

2. Keep the receiver enable output (RE) active and

receive subsequent message codewords, until any of

the call termination criteria are fulfilled.

3. Trigger the serial message transfer by sending a start

condition and transfer deformatted message

codewords as attached to the address codeword via

the serial microcontroller interface to an external

microcontroller, followed by a stop condition.

Normally call termination is assumed, when a valid idle or

address codeword is received. On reception of

uncorrectable codewords, call termination takes place in

accordance with conditions shown in Table 2.

Table 2

Call termination on error

Note

1. X = don’t care.

SPF12

SPF13

CALL TERMINATION EVENT

0X(1)

Any two consecutive codewords or the codeword directly following the address

codeword uncorrectable.

Any single codeword uncorrectable.

Any two consecutive codewords uncorrectable.

PCF5001 Datasheet(PDF) 13 Page - NXP Semiconductors

PCF5001 Datasheet(HTML) 13 Page - NXP Semiconductors

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44

Datasheet Download

Link URL