PCD5003AH Philips Semiconductors, PCD5003AH Datasheet - Page 7

• Manufacturer Part Number: PCD5003AH
• Description: Enhanced Pager Decoder for POCSAG
• Manufacturer: Philips Semiconductors

Philips Semiconductors
Alert-only calls only consist of a single address code-word.
Numeric and alphanumeric calls have message
code-words following the address. A message causes the
frame structure to be temporarily suspended. Message
code-words are sent until the message is completed, with
only the sync words being transmitted in their expected
positions.
Message code-words 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 code-word 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 code-word.
1999 Jan 08
handbook, full pagewidth
Enhanced Pager Decoder for POCSAG
10101 . . . 10101010
PREAMBLE
Address code-word
Message code-word
BATCH 1
Fig.3 POCSAG code structure.
SYNC | CW CW | CW CW | . . . . . | CW CW
BATCH 2
0 18-bit address
1 20-bit message
FRAME 0
7
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 PCD5003A. Message data is not
deformatted.
In the PCD5003A error correction methods have been
implemented as shown in Table 2.
Random error correction is default for both address and
message code-words. In addition, burst error correction
can be enabled by SPF programming. Up to 3 erroneous
bits in a 4-bit burst can be corrected.
The error type detected for each code-word is identified in
the message data output to the microcontroller, allowing
rejection of calls with too many errors.
BATCH 3
FRAME 1
2 function bits
FRAME 7
10 CRC bits
10 CRC bits
LAST BATCH
MCD456
P
P
Product specification
PCD5003A