PCD5002 Datasheet, PDF (13/48 Pages) NXP Semiconductors – Advanced POCSAG and APOC-1 Paging Decoder

Philips Semiconductors
Advanced POCSAG and APOC-1 Paging
Decoder
Product specification
PCD5002
If valid codewords are detected but no sync word or
preamble is detected over a period of 18 codewords, the
receiver is also disabled.
Data sampling, as previously described, is repeated one
cycle duration after the moment the receiver was last
activated.
8.15 Call termination
Call reception is terminated:
• Upon reception of any address codeword (including Idle
codeword but excluding the batch zero identifier in
APOC-1 operation) requiring no more than single bit
error correction
• In ‘data fail’ mode, when a sync word is not detected at
the expected batch position
• When a forced call termination command is received
from an external controller.
The last method permits an external controller to stop call
reception, depending on the number and type of errors
which occurred in a call. After a forced call termination the
decoder will enter the ‘data fail’ mode.
The type of error correction as well as the call termination
conditions are indicated by status bits in the message data
output.
Following call termination, transfer of the data received
since the previous sync word period is initiated by an
interrupt to the external controller.
8.16 Call data output format
POCSAG call information is stored in the decoder SRAM
in blocks of 3 bytes per codeword. Each stored call
consists of a call header, followed by message data blocks
and a call terminator. In the event of concatenated
messages the call terminator is replaced with the call
header of the next message. An alert-only call only has a
call header and a call terminator.
The formats of a call header, a message data block and a
call terminator are shown in Tables 5, 7 and 9.
A Call Header contains information on the last sync word
received, the RIC which began call reception and the type
of error correction performed on the address codeword.
A Message Data block contains the data bits from a
message codeword plus the type of error correction
performed. No deformatting is performed on the data bits:
numeric data appear as 4-bit groups per digit,
alphanumeric data has a 7-bit ASCII representation.
The Call Terminator contains information on the last sync
word received, information on the way the call was
terminated (forced call termination command, loss of sync
word in ‘data fail’ mode) and the type of error correction
performed on the terminating codeword.
8.17 Error type indication
Table 11 shows how the different types of detected errors
are encoded in the call data output format.
A message codeword containing more than a single bit
error (bit E3 = 1) may appear as an address codeword
(bit M1 = 0) after error correction. In this event the
codeword is processed as message data and does not
cause call termination.
8.18 Data transfer
Data transfer is initiated either during sync word periods or
as soon as the receiver is disabled after call termination.
If the SRAM buffer is full, data transfer is initiated
immediately during the next codeword.
When the PCD5002 is ready to transfer received call data
an external interrupt will be generated via output INT.
Any message data can be read by accessing the RAM
output register via the I²C-bus interface. Bytes will be
output starting from the position indicated by the RAM read
pointer.
1997 Jun 24
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