PCD5002AH datasheet(13/48 Pages) PHILIPS

13 / 48 page

1999 Jan 08

Philips Semiconductors

Product speciﬁcation

Enhanced Pager Decoder for

APOC1/POCSAG

PCD5002A

Detection of preamble will cause the device to switch to the

‘preamble receive’ mode, while sync word detection will

cause the device to switch to the ‘batch zero detect’ mode.

When neither is detected during the 2 code-word window

or any following 32-bit group, the receiver will be disabled.

If valid code-words are detected but no sync word or

preamble is detected over a period of 18 code-words, 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 code-word (including idle

code-word but excluding the batch zero identifier in

APOC1 operation) requiring no more than single bit

error correction

• Upon reception of a correctable address code-word

(error type other than ‘111’; see Table 11) that matches

an enabled RIC

• When a forced call termination command is received

from an external controller.

• In ‘data fail’ mode, when a sync word is not detected at

the expected batch position.

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.

In the event of the terminating code-word matching an

enabled RIC, a concatenated call will be started with the

call header replacing the terminator of the previous call.

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

Enhanced call termination

The PCD5002A provides an enhanced mode of call

termination which is enabled by setting SPF byte 3, bit D7.

When enabled, the following call termination conditions

applies, in addition to those listed in Section 8.15.

• Reception of two consecutive code-words (excluding

sync word), each of which are either uncorrectable or an

address code-word with more than one bit in error.

8.17

Call data output format

POCSAG call information is stored in the decoder SRAM

in blocks of 3 bytes per code-word. 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 code-word.

A Message Data block contains the data bits from a

message code-word 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 code-word.

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