PCD5002 Просмотр технического описания (PDF) - Philips Electronics
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PCD5002 Datasheet PDF : 48 Pages
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Philips Semiconductors
Advanced POCSAG and APOC-1 Paging
Decoder
Product specification
PCD5002
Table 1 POCSAG recommended call types and function bits
BIT 20 (MSB)
0
0
1
1
BIT 21 (LSB)
0
1
0
1
CALL TYPE
numeric
alert only 1
alert only 2
alphanumeric
DATA FORMAT
4-bits per digit
−
−
7-bits per ASCII character
The POCSAG standard only allows combinations of data
formats and function code bits as given in Table 1.
However, other (non-standard) combinations will be
decoded normally by the PCD5002.
8.4 Error correction
In the PCD5002 error correction methods have been
implemented as shown in Table 2.
Random error correction is default for both address and
message codewords. 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 codeword is identified in
the message data output to the microcontroller, allowing
rejection of calls with too many errors.
Table 2 Error correction
ITEM
Preamble
Synchronization
codeword
Address codeword
Message codeword
CORRECTION
4 random errors in 31 bits
2 random errors in 32 bits
2 random errors, plus 4-bit burst
errors (optional)
2 random errors, plus 4-bit burst
errors (optional)
8.5 Operating states
The PCD5002 has 2 operating states:
• ON status
• OFF status.
The operating state is determined by a Direct Control input
(DON) and bit D4 in the control register (see Table 3).
Table 3 Truth table for decoder operating status
DON
INPUT
0
0
1
1
CONTROL
BIT D4
0
1
0
1
OPERATING STATUS
OFF
ON
ON
ON
8.6 ON status
In the ON status the decoder pulses the receiver and
oscillator enable outputs (RXE and ROE respectively)
according to the code structure and the synchronization
algorithm. Data received serially at the data input (RDI) is
processed for call reception.
The data protocol can be POCSAG or APOC-1.
Continuous data decoding upon reception of a special
sync word is also supported. The data protocol is selected
by SPF programming.
Reception of a valid paging call is signalled to the
microcontroller by an interrupt signal. The received
address and message data can then be read via the
I2C-bus interface.
8.7 OFF status
In the OFF status the decoder will neither activate the
receiver or oscillator enable outputs, nor process any data
at the data input. The crystal oscillator remains active to
permit communication with the microcontroller.
In both operating states an accurate timing reference is
available via the REF output. Using SPF programming the
signal periodicity may be selected as 32.768 kHz, 50 Hz,
2 Hz or 1⁄60 Hz.
8.8 Reset
The decoder can be reset by applying a positive pulse on
input pin RST. For successful reset at power-on, a HIGH
level must be present on the RST pin while the device is
powering-up.
1997 Jun 24
8
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