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| 型號(hào)： | PCD5008 |
| 廠商： | NXP Semiconductors N.V. |
| 英文描述： | FLEX Pager Decoder |
| 中文描述： | FleX創(chuàng)建傳呼機(jī)解碼器 |
| 文件頁數(shù)： | 51/64頁 |
| 文件大小： | 341K |
| 代理商： | PCD5008 |
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1998 Jun 17
51
Philips Semiconductors
Product specification
FLEX
Pager Decoder
PCD5008
8.8.5
M
ESSAGE FRAGMENTATION
The FLEX
frame length limits the maximum number of
message codewords that can be associated with an
address codeword. Messages longer than 84 codewords
must be sent as several fragments. The PCD5008
uses AFM (Section 8.8.3) to allow the reception of
fragmented messages.
The fragments of a message are sent in sequence. Each
fragment contains a checksum character to detect errors
in the fragment, a message number to identify which
message the fragment is a part, and the continue bit which
either indicates that more fragments are in queue or that
the last fragment has been received. Each fragment also
contains a fragment number starting with 3 for the first
fragment and then incremented through the
sequence 0, 1 or 2 in subsequent fragments. This allows
the detection of missing fragments.
Message fragments may not be separated by more than
32 frames (1 minute) or 128 frames (4 minutes), as
indicated by the service provider. During the reception of a
fragmented message, the PCD5008 examines every
frame for additional fragments until the last fragment is
encountered or the host determines that more than
32 or 128 frames have elapsed since the reception of the
previous message fragment.
The sequence for the host and the PCD5008 to receive a
fragmented message is as follows:
1.
The PCD5008 receives an address codeword followed
by a vector indicating one of:
a) Secure (vector type = 000)
b) Alphanumeric (vector type = 101)
c) Hexadecimal/binary (vector type = 110).
The PCD5008 passes the address, vector and
message codewords to the host as packets and
increments its internal AFM counter and enters AFM.
2.
While in AFM, the PCD5008 decodes all of the frames
passing any address, vector and message information
to the host followed by a status packet indicating the
end of each frame and the current frame number.
3.
Every time the host receives a secure, alphanumeric
or hexadecimal/binary vector packet, it inspects the
message continued flag (C) in the first message
packet:
a) If this is not a fragmented message (C is clear and
no fragmented messages are in progress for this
address and message number), then the host
decrements the AFM counter by sending an
AFM packet to the PCD5008 with the DAF bit set.
If the fragmented message was received on a
temporary address, then the appropriate DTA bit
should also be set in the AFM packet.
b) If this is the first fragment of a fragmented message
(C is set and no fragmented messages are in
progress for this address and message number),
then the host does not decrement the AFM counter
and expects further fragments to be received for
this address in subsequent frames.
c) If this is the second or subsequent fragment of a
fragmented message and further fragments will
follow, (C is set and a fragmented message is in
progress for this address and message number),
then the host decrements the AFM counter by
sending an AFM packet to the PCD5008 with the
DAF bit set.
d) If this is the last fragment of a fragmented
message, (C is clear and a fragmented message is
in progress for this address and message number),
then the host decrements the AFM counter by 2,
sending 2 AFM packets to the PCD5008 with the
DAF bit set. If the fragmented message was
received on a TA, then one of these AFM packets
should also have the appropriate DTA bit set.
If, on receiving a status packet, the host determines
that more than 32 or 128 frames have elapsed since
the reception of a fragment for a fragmented message
then the host decrements the AFM counter by sending
an AFM packet to the PCD5008 with the DAF bit set.
If the fragmented message was received on a TA, then
the appropriate DTA bit should also be set in the
AFM packet.
When no fragmented messages are in progress
(the AFM counter = 0) and no TAs are pending
(all TA counters = 0) and the FAF bit is clear in the
AFM packet, the PCD5008 leaves AFM.
4.
5.
As an alternative to the above scheme, the host may
choose to decrement the AFM counter at the end of the
entire message by decrementing it once for each fragment
received. This method is limited to a maximum of
127 fragments.
Tables 57 and 58 show examples of message reception
with and without message fragmentation.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| PCD5008H | FLEX Pager Decoder |
| PCD5013 | FLEX roaming decoder II |
| PCD5013H | FLEX roaming decoder II |
| PCD5032 | ADPCM CODEC for digital cordless telephones |
| PCD5032H | ADPCM CODEC for digital cordless telephones |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| PCD5008H | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:FLEX Pager Decoder |
| PCD5008HBD-T | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Telecommunication Decoder |
| PCD5013 | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:FLEX roaming decoder II |
| PCD5013H | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:FLEX roaming decoder II |
| PCD5032 | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:ADPCM CODEC for digital cordless telephones |
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