PCD5002 datasheet(15/48 Pages) PHILIPS

15 / 48 page

1997 Jun 24

Philips Semiconductors

Product speciﬁcation

Advanced POCSAG and APOC-1 Paging

Decoder

PCD5002

Table 10 Call terminator bit identiﬁcation

Note

1. The DF bit in the call terminator is set:

a) When any call data codeword in the terminating batch was uncorrectable, while in ‘data receive’ mode.

b) When the sync word at the start of the terminating batch did not match the standard POCSAG or a

user-programmed sync word, while in ‘data fail’ mode.

Table 11 Error type identiﬁcation (note 1)

Note

1. POCSAG code allows a maximum of 3 bit errors to be detected per codeword.

BITS (MSB to LSB)

IDENTIFICATION

forced call termination (1 = yes)

S3 to S1

identifier number of last sync word

data fail mode indication (1 = data fail mode); note 1

F0 and F1

function bits of received address codeword (bits 20 and 21)

E3 to E1

detected error type; see Table 11; E3 = 0 in a call terminator

ERROR TYPE

NUMBER OF ERRORS

no errors - correct codeword

parity bit in error

single bit error

1 + parity

single bit error and parity error

not used

−

4-bit burst error and parity error

3 (e.g.1101)

2-bit random error

uncorrectable codeword

3 or more

Successful call termination occurs on reception of a valid

address codeword with less than 2 bit errors.

Unsuccessful termination occurs when a sync word is not

detected while in the ‘data fail’ mode.

It is generally possible to distinguish these two conditions

using the sync word identifier number (bits S3 to S1); the

identifier number will be non-zero for correct termination,

and zero for sync word failure.

Only when a call is received in the ‘data fail’ mode and the

call is terminated before the end of the batch, is it not

possible to distinguish unsuccessful from successful

termination.

Reception of message data can be terminated at any time

by transmitting a forced call termination command to the

status register via the I2C-bus. Any call received will then

be terminated immediately and the ‘data fail’ mode will be

entered.

8.19

Continuous data decoding

Apart from transmissions in the POCSAG or APOC-1

format, the PCD5002 is also capable of decoding

continuous transmissions with the same codeword

structure. Any user-programmable sync word (UPSW)

may be designated to enable continuous data decoding.

When a Continuous Data Decoding (CDD) sync word is

detected at any sync word position, the receiver remains

enabled from then on. Status bits D1 and D0 show the

CDD mode to be active.

All codewords are decoded and their data fields are stored

in SRAM. The usual error information is appended. No

distinction is made between address and message

codewords: codeword bit 0 is treated as a data bit and is

stored in bit M1 of the 3-byte output format.

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