PCD5003 Ver la hoja de datos (PDF) - Philips Electronics
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PCD5003 Datasheet PDF : 44 Pages
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Philips Semiconductors
Advanced POCSAG Paging Decoder
Product specification
PCD5003
7.3 Error correction
Table 2 Error correction
ITEM
Preamble
Synchronization codeword
Address codeword
Message codeword
DESCRIPTION
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)
In the PCD5003 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.
7.6 OFF status
In 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. By SPF programming the
signal periodicity may be selected as 32.768 kHz, 50 Hz,
2 Hz or 1⁄60 Hz.
7.4 Operating states
The PCD5003 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
7.5 ON status
In ON status the decoder pulses the receiver and oscillator
enable outputs (respectively RXE and ROE) according to
the code structure and the synchronization algorithm. Data
received serially at the data input (RDI) is processed for
call receipt. Reception of a valid paging call is signalled to
the microcontroller by means of an interrupt signal.
The received address and message data can then be read
via the I2C-bus interface.
7.7 Reset
The decoder can be reset by applying a positive pulse on
input pin RST. A power-on reset circuit consisting of an RC
network can be connected to this input as well. Conditions
during and after a reset are described in Chapter
“Operating instructions”.
For successful reset at power-on, a HIGH level must be
present on the RST pin while the device is powering-up.
This can be applied by the microcontroller, or via a suitable
RC power-on reset circuit connected to the RST input.
Reset circuit details and conditions during and after a reset
are described in Chapter 8
7.8 Bit rates
The PCD5003 can be configured for data rates of 512,
1200 or 2400 bit/s by SPF programming. These data
rates are derived from a single 76.8 kHz oscillator
frequency.
7.9 Oscillator
The oscillator circuit is designed to operate at 76.8 kHz.
Typically, a tuning fork crystal will be used as a frequency
source. Alternatively, an external clock signal can be
applied to pin XTAL1 (amplitude = VDD to VSS), but a
slightly higher oscillator current is consumed. A 2.2 MΩ
feedback resistor connected between XTAL1 and XTAL2
is required for proper operation.
1997 Jun 24
8
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