PCD5002 datasheet(13/48 Pages) PHILIPS

13 / 48 page

1997 Jun 24

Philips Semiconductors

Product speciﬁcation

Advanced POCSAG and APOC-1 Paging

Decoder

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.

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