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PCD5003

Advanced POCSAG Paging Decoder

Philips Electronics 

Philips Semiconductors

Advanced POCSAG Paging Decoder

Product specification

PCD5003

Alert-only calls only consist of a single address codeword.

Numeric and alphanumeric calls have message

codewords following the address. A message causes the

frame structure to be temporarily suspended. Message

codewords are sent until the message is completed, with

only the sync words being transmitted in their expected

positions.

Message codewords are identified by an MSB of logic 1

and are coded as shown in Fig.3. The message

information is stored in a 20-bit field (bits 2 to 21). The data

format is determined by the call type: 4 bits per digit for

numeric messages and 7 bits per (ASCII) character for

alphanumeric messages.

Each codeword is protected against transmission errors by

10 CRC check bits (bits 22 to 31) and an even-parity bit

(bit 32). This permits correction of maximum 2 random

errors or up to 3 errors in a burst of 4 bits (a 4-bit burst

error) per codeword.

The POCSAG standard recommends the use of

combinations of data formats and function bits, as given in

Table 1. Other (non-standard) combinations will be

received normally by the PCD5003. Message data is not

deformatted.

handbook, full pagewidth

PREAMBLE BATCH 1

BATCH 2

BATCH 3

LAST BATCH

10101 . . . 10101010

SYNC | CW CW | CW CW | . . . . . | CW CW

FRAME 0 FRAME 1

FRAME 7

Address code-word 0 18-bit address 2 function bits 10 CRC bits P

Message code-word 1 20-bit message

10 CRC bits P

MCD456

Fig.3 POCSAG code structure.

Table 1 POCSAG recommended call types and function bits

BIT 20 (MSB)

0

0

1

1

BIT 21 (LSB)

0

1

0

1

CALL TYPE

numeric

alert only 1

alert only 2

alphanumeric

DATA FORMAT

4-bits per digit

−

−

7-bits per ASCII character

1997 Jun 24

7

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