Philips PCD5002AH-F1 Datasheet

DATA SH EET

Product speciﬁcation File under Integrated Circuits, IC17

1999 Jan 08

INTEGRATED CIRCUITS

PCD5002A

Enhanced Pager Decoder for APOC1/POCSAG

1999 Jan 08 2

Philips Semiconductors Product speciﬁcation

Enhanced Pager Decoder for APOC1/POCSAG

PCD5002A

CONTENTS

1 FEATURES 2 APPLICATIONS 3 GENERAL DESCRIPTION 4 ORDERING INFORMATION 5 LICENSE 6 BLOCK DIAGRAM 7 PINNING 8 FUNCTIONAL DESCRIPTION

8.1 Introduction

8.2 The POCSAG paging code

8.3 The APOC1 paging code

8.4 Error correction

8.5 Operating states

8.6 ON status

8.7 OFF status

8.8 Reset

8.9 Bit rates

8.10 Oscillator

8.11 Input data processing

8.12 Battery saving

8.13 POCSAG synchronization strategy

8.14 APOC1 synchronization strategy

8.15 Call termination

8.16 Enhanced call termination

8.17 Call data output format

8.18 Error type indication

8.19 Data transfer

8.20 Continuous data decoding

8.21 Receiver and oscillator control

8.22 Demodulator quick charge

8.23 External receiver control and monitoring

8.24 Battery condition input

8.25 Synthesizer control

8.26 Serial microcontroller interface

8.27 Decoder I2C-bus access

8.28 External interrupt

8.29 Interrupt masking

8.30 Status/control register

8.31 Pending interrupts

8.32 Out-of-range indication

8.33 Real-time clock

8.34 Periodic interrupt

8.35 Received call delay

8.36 Alert generation

8.37 Alert cadence register (03H; write)

8.38 Acoustic alert

8.39 Vibrator alert

8.40 LED alert

8.41 Warbled alert

8.42 Direct alert control

8.43 Alert priority

8.44 Cancelling alerts

8.45 Automatic POCSAG alerts

8.46 SRAM access

8.47 RAM write address pointer (06H; read)

8.48 RAM read address pointer (08H; read/write)

8.49 RAM data output register (09H; read)

8.50 EEPROM access

8.51 EEPROM address pointer (07H; read/write)

8.52 EEPROM data I/O register (0AH; read/write)

8.53 EEPROM access limitations

8.54 EEPROM read operation

8.55 EEPROM write operation

8.56 Invalid write address

8.57 Incomplete programming sequence

8.58 Unused EEPROM locations

8.59 Special programmed function allocation

8.60 Synthesizer programming data

8.61 Identifier storage allocation

8.62 Voltage doubler

8.63 Level-shifted interface

8.64 Signal test mode 9 OPERATING INSTRUCTIONS

9.1 Reset conditions

9.2 Power-on reset circuit

9.3 Reset timing

9.4 Initial programming 10 LIMITING VALUES 11 DC CHARACTERISTICS 12 DC CHARACTERISTICS (WITH VOLTAGE

CONVERTER) 13 OSCILLATOR CHARACTERISTICS 14 AC CHARACTERISTICS 15 APPLICATION INFORMATION 16 PACKAGE OUTLINE 17 SOLDERING

17.1 Introduction to soldering surface mount

packages

17.2 Reflow soldering

17.3 Wave soldering

17.4 Manual soldering

17.5 Suitability of surface mount IC packages for

wave and reflow soldering methods 18 DEFINITIONS 19 LIFE SUPPORT APPLICATIONS 20 PURCHASE OF PHILIPS I2C COMPONENTS

1999 Jan 08 3

Philips Semiconductors Product speciﬁcation

Enhanced Pager Decoder for APOC1/POCSAG

PCD5002A

1 FEATURES

• Wide operating supply voltage range: 1.5 to 6.0 V

• EEPROM programming requires only 2.0 V supply

• Low operating current: 50 µA typ. (ON), 25 µA typ.

(OFF)

• Temperature range −25 to +70 °C

•

“CCIR radio paging Code No. 1”

(POCSAG) compatible

• Supports Advanced Pager Operator’s Code Phase 1 (APOC1) for extended battery economy

• 512, 1200 and 2400 bits/s data rates using 76.8 kHz crystal

• Built-in data filter (16 times oversampling) and bit clock recovery

• Advanced ACCESS



synchronization algorithm

• 2-bit random and (optional) 4-bit burst error correction

• Up to 6 user addresses Receiver Identity Codes (RICs),

each with 4 functions/alert cadences

• Optional automatic call termination when bit error rate is high

• Up to 6 user address frames, independently programmable

• Standard POCSAG sync word, plus up to 4 user programmable sync words

• Continuous data decoding upon reception of user programmable sync word (optional)

• Received data inversion (optional)

• Call alert via beeper, vibrator or LED

• 2-level acoustic alert using single external transistor

• Alert control: automatic (POCSAG type), via cadence

• Separate power control of receiver and RF oscillator for battery economy

• Dedicated pin for easy control of superheterodyne receiver

• Synthesizer set-up and control interface (3-line serial)

• On-chip EEPROM for storage of user addresses (RICs),

pager configuration and synthesizer data

• On-chip SRAM buffer for message data

• Slave I

C-bus interface to microcontroller for transfer of message data, status/control and EEPROM programming (data transfer at up to 100 kbits/s)

• Wake-up interrupt for microcontroller, programmable polarity

• Direct and I2C-bus control of operating status (ON/OFF)

• Battery-low indication (external detector)

• Out-of-range condition indication

• Real-time clock reference output

• On-chip voltage doubler

• Interfaces directly to UAA2080 and UAA2082 paging

receivers.

2 APPLICATIONS

• Advanced display pagers (POCSAG and APOC1)

• Basic alert-only pagers

• Information services

• Personal organizers

• Telepoint

• Telemetry/data transmission.

3 GENERAL DESCRIPTION

The PCD5002A is a very low power pager decoder and controller, capable of handling both standard POCSAG and the advanced APOC1 code. Continuous data decoding upon reception of a dedicated sync word is available for news pager applications.

Data rates supported are 512, 1200 and 2400 bits/s using a single 76.8 kHz crystal. On-chip EEPROM is programmable using a minimum supply voltage of 2.0 V, allowing ‘over-the-air’ programming. I

C-bus compatible.

4 ORDERING INFORMATION

TYPE NUMBER

PACKAGE

NAME DESCRIPTION VERSION

PCD5002AH LQFP32 plastic low proﬁle quad ﬂat package; 32 leads; body 7 × 7 × 1.4 mm SOT358-1

1999 Jan 08 4

Philips Semiconductors Product speciﬁcation

Enhanced Pager Decoder for APOC1/POCSAG

PCD5002A

5 LICENSE

Supply of this IC does neither convey nor express an implied license under any patent right to use this in any APOC application.

6 BLOCK DIAGRAM

Fig.1 Block diagram.

handbook, full pagewidth

MGL563

SYNTHESIZER

CONTROL

ZSD ZSC

ZLE

26 27 28

RECEIVER

CONTROL

RXE

ROE

DATA FILTER

AND

CLOCK

RECOVERY

RDI

MAIN DECODER

DECODING

DATA

CONTROL

POCSAG

SYNCHRONIZATION

EEPROM CONTROL

EEPROM

RAM

CONTROL

RAM

RESET

SET-UP

C-BUS

CONTROL

REGISTERS

AND

INTERRUPT

CONTROL

ALERT

GENERATION

AND

CONTROL

VOLTAGE DOUBLER

AND LEVEL

SHIFTER

PCD5002A

TIMER

REFERENCE

MASTER DIVIDER

CLOCK

CONTROL

TEST

CONTROL

OSCILLATOR

DON

TS1

TS2

XTAL1

XTAL2

VDDV

n.c.

12, 291119, 6

RST

SDA

SCL

INT

BAT

LED

ATL

ATH

ALC

REF

CCN

CCP

14 13

DQC

VIB

1999 Jan 08 5

Philips Semiconductors Product speciﬁcation

Enhanced Pager Decoder for APOC1/POCSAG

PCD5002A

7 PINNING

SYMBOL PIN DESCRIPTION

ATL 1 alert LOW level output ALC 2 alert control input (normally LOW by

internal pull-down)

DON 3 direct ON/OFF input (normally LOW by

internal pull-down)

REF 4 real-time clock frequency reference

output INT 5 interrupt output n.c. 6 not connected RST 7 reset input (normally LOW by internal

pull-down) V

8 external positive voltage reference

input SDA 9 I

C-bus serial data input/output

SCL 10 I

C-bus serial clock input

11 main positive supply voltage

12 main negative supply voltage

13 voltage converter positive output

CCP 14 voltage converter shunt capacitor

(positive side) CCN 15 voltage converter shunt capacitor

(negative side)

TS1 16 test input1 (normally LOW by internal

pull-down) XTAL2 17 decoder crystal oscillator output XTAL1 18 decoder crystal oscillator input n.c. 19 not connected TS2 20 test input2 (normally LOW by internal

pull-down) BAT 21 battery sense input DQC 22 demodulator quick charge output RDI 23 received data input (POCSAG or

APOC1) RXE 24 receiver circuit enable output ROE 25 receiver oscillator enable output ZSD 26 synthesizer serial data output ZSC 27 synthesizer serial clock output ZLE 28 synthesizer latch enable output V

29 main negative supply voltage VIB 30 vibrator motor drive output LED 31 LED drive output ATH 32 alert HIGH level output

SYMBOL PIN DESCRIPTION

Fig.2 Pin configuration.

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1 2 3 4 5 6 7 8

24 23 22 21 20 19 18 17

ATH

LED

VIB

ZLE

ZSC

ZSD

ROE

SDA

SCL

CCP

CCN

TS1

ATL

ALC

DON

REF

INT n.c.

RST

RXE RDI DQC BAT TS2 n.c. XTAL1 XTAL2

PCD5002AH

MGL564

1999 Jan 08 6

Philips Semiconductors Product speciﬁcation

Enhanced Pager Decoder for APOC1/POCSAG

PCD5002A

8 FUNCTIONAL DESCRIPTION

8.1 Introduction

The PCD5002A is a very low power decoder and pager controller specifically designed for use in new generation radio pagers. The architecture of the PCD5002A allows for flexible application in a wide variety of radio pager designs.

The PCD5002A is fully compatible with

“CCIR Radio

paging Code No. 1”

(also known as the POCSAG code) operating at data rates of 512, 1200 and 2400 bits/s using a single oscillator crystal of 76.8 kHz.

The PCD5002A also supports the new Advanced Pager Operator’s Code Phase 1 (APOC1). This compatible extension to the POCSAG code improves battery economy by introducing ‘cycles’ and batch numbering. A cycle consists of 5 or 15 standard POCSAG batches. Each pager will be allocated a batch number in addition to its POCSAG address and it will only search for its address during this batch.

In addition to the standard POCSAG sync word (used also in APOC1) the PCD5002A is also capable of recognizing up to 4 User Programmable Sync Words (UPSWs). This permits the reception of both private services and POCSAG or APOC1 transmissions via the same radio channel. As an option reception of a UPSW may activate Continuous Data Decoding (CDD).

Used together with the Philips UAA2080 or UAA2082 paging receiver, the PCD5002A offers a highly sophisticated, miniature solution for the radio paging market. Control of an RF synthesizer circuit is also provided to ease alignment and channel selection.

On-chip EEPROM provides storage for user addresses (Receiver Identity Codes or RICs) and Special Programmed Functions (SPFs) and UPSWs, which eliminates the need for external storage devices and interconnection. For other non-volatile storage 20 bytes of general purpose EEPROM are available. The low EEPROM programming voltage makes the PCD5002A well suited for ‘over-the-air’ programming/reprogramming.

On request from an external controlling device or automatically (by SPF programming), the PCD5002A will provide standard POCSAG alert cadences by driving a standard acoustic ‘beeper’. Non-standard alert cadences may be generated via a cadence register or a dedicated control input.

The PCD5002A can also produce a HIGH level acoustic alert as well as drive an LED indicator and a vibrator motor via external bipolar transistors.

The PCD5002A contains a low-power, high-efficiency voltage converter (doubler) designed to provide a higher voltage supply to LCD drivers or microcontrollers. In addition, an independent level shifted interface is provided allowing communication to a microcontroller operating at a higher voltage than the PCD5002A.

Interface to such an external device is provided by an I

C-bus which allows received call identity and message data, data for the programming of the internal EEPROM, alert control and pager status information to be transferred between the devices. Pager status includes features provided by the PCD5002A such as battery-low and out-of-range indications. A dedicated interrupt line minimizes the required microcontroller activity.

A selectable low frequency timing reference is provided for use in real-time clock functions.

Data synchronization is achieved by the Philips patented ACCESS algorithm ensuring that maximum advantage is made of the POCSAG code structure particularly in fading radio signal conditions. The algorithm allows for data synchronization without preamble detection whilst minimizing battery power consumption. The APOC1 code uses an extended version of the ACCESS



synchronization algorithm. Random (and optional) burst error correction techniques

are applied to the received data to optimize the call success rate without increasing the falsing rate beyond specified POCSAG levels.

8.2 The POCSAG paging code

A transmission using the

“CCIR Radio paging Code No. 1”

(POCSAG code) is constructed in accordance with the following rules (see Fig.3).

The transmission is started by sending a preamble, consisting of at least 576 continuously alternating bits (10101010...). The preamble is followed by an arbitrary number of batch blocks. Only complete batches are transmitted.

Each batch comprises 17 code-words of 32 bits each. The first code-word is a synchronization code-word with a fixed pattern. The sync word is followed by 8 frames (0 to 7) of 2 code-words each, containing message information. A code-word in a frame can either be an address, message or idle code-word.

Idle code-words also have a fixed pattern and are used to fill empty frames or to separate messages.

1999 Jan 08 7

Philips Semiconductors Product speciﬁcation

Enhanced Pager Decoder for APOC1/POCSAG

PCD5002A

Address code-words are identified by an MSB at logic 0 and are coded as shown in Fig.3. A user address or RIC consists of 21 bits. Only the upper 18 bits are encoded in the address code-word (bits 2 to 19). The lower 3 bits designate the frame number (0 to 7) in which the address is transmitted.

Four different call types (‘numeric’, ‘alphanumeric’ and two ‘alert only’ types) can be distinguished. The call type is determined by two function bits in the address code-word (bits 20 and 21), as shown in Table 1.

Alert-only calls consist only of a single address code-word. Numeric and alphanumeric calls have message code-words following the address. A message causes the frame structure to be temporarily suspended. Message code-words are sent until the message is completed, with only the sync words being transmitted in their expected positions.

Message code-words are identified by an MSB at logic 1 and are coded as shown in Fig.3. The message information is stored in a 20-bit field (bits 2 to 21).

The standard data format is determined by the call type: 4 bits per digit for numeric messages and 7 bits per (ASCII) character for alphanumeric messages.

Each code-word is protected against transmission errors by 10 CRC check bits (bits 22 to 31) and an even-parity bit (bit 32).

This permits correction of a maximum of 2 random errors or up to 3 errors in a burst of 4 bits (a 4-bit burst error) per code-word.

8.3 The APOC1 paging code

The APOC1 paging code is fully POCSAG compatible and involves the introduction of batch grouping and a Batch Zero Identifier (BZI). This reserved address code-word indicates the start of a ‘cycle’ of 5 or 15 batches long and is transmitted immediately after a sync word.

Cycle transmission must be coherent i.e. a transmission starting an integer number of cycle periods after the start of the previous one.

Broadcast message data may be included in a transmission. This information may occupy any number of message code-words and immediately follows the batch zero identifier of the first cycle after preamble. The presence of data is indicated by the function bits in the batch zero identifier: 1,1 indicates ‘no broadcast data’. Any other combination indicates a broadcast message.

The PCD5002A can be configured for POCSAG or APOC1 operation via SPF programming. The batch zero identifier is programmable and can be stored in any identifier location in EEPROM.

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 PCD5002A.

Fig.3 POCSAG code structure.

handbook, full pagewidth

PREAMBLE BATCH 1 BATCH 2 BATCH 3 LAST BATCH

SYNC | CW CW | CW CW | . . . . . | CW CW

FRAME 0 FRAME 1 FRAME 7

10101 . . . 10101010

Address code-word

Message code-word

0 18-bit address 2 function bits 10 CRC bits P

1 20-bit message 10 CRC bits P

MCD456

1999 Jan 08 8

Philips Semiconductors Product speciﬁcation

Enhanced Pager Decoder for APOC1/POCSAG

PCD5002A

Table 1 POCSAG recommended call types and function bits

BIT 20 (MSB) BIT 21 (LSB) CALL TYPE DATA FORMAT

0 0 numeric 4-bits per digit 0 1 alert only 1 − 1 0 alert only 2 − 1 1 alphanumeric 7-bits per ASCII character

8.4 Error correction

In the PCD5002A error correction methods have been implemented as shown in Table 2.

Random error correction is default for both address and message code-words. 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 code-word is identified in the message data output to the microcontroller, allowing rejection of calls with too many errors.

Table 2 Error correction

8.5 Operating states

The PCD5002A 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

ITEM CORRECTION

Preamble 4 random errors in 31 bits Synchronization

code-word

2 random errors in 32 bits

Address code-word 2 random errors; plus 4-bit burst

errors (optional)

Message code-word 2 random errors; plus 4-bit burst

errors (optional)

DON

INPUT

CONTROL

BIT D4

OPERATING STATUS

0 0 OFF 01 ON 10 ON 11 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 APOC1. 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 I

C-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

⁄60Hz.

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.

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 9.

1999 Jan 08 9

Philips Semiconductors Product speciﬁcation

Enhanced Pager Decoder for APOC1/POCSAG

PCD5002A

8.9 Bit rates

The PCD5002A can be configured for data rates of 512, 1200 or 2400 bits/s by SPF programming. These data rates are derived from a single 76.8 kHz oscillator frequency.

8.10 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 = V

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.

To allow easy oscillator adjustment (e.g. by a variable capacitor) a 32.768 kHz reference frequency can be selected at output REF by SPF programming.

8.11 Input data processing

Data input is binary and fully asynchronous. Input bit rates of 512, 1200 and 2400 bits/s are supported. As a programmable option, the polarity of the received data can be inverted before further processing.

The input data is noise filtered by a digital filter. Data is sampled at 16 times the data rate and averaged by majority decision.

The filtered data is used to synchronize an internal clock generator by monitoring transitions. The recovered clock phase can be adjusted in steps of

⁄8or1⁄32bit period per

received bit. The larger step size is used when bit synchronization has

not been achieved, the smaller when a valid data sequence has been detected (e.g. preamble or sync word).

8.12 Battery saving

Current consumption is reduced by switching off internal decoder sections whenever the receiver is not enabled.

To further increase battery efficiency, reception and decoding of an address code-word is stopped as soon as the uncorrected address field differs by more than 3 bits from the enabled RICs. If the next code-word must be received again, the receiver is re-enabled thus observing the programmed establishment times t

RXE

and t

ROE

The current consumption of the complete pager can be minimized by separately activating the RF oscillator circuit (using output ROE) before activating the rest of the receiver. This is possible using the UAA2082 receiver which has external biasing for the oscillator circuit.

8.13 POCSAG synchronization strategy

In the ON status the PCD5002A synchronizes to the POCSAG data stream by the Philips ACCESS



algorithm. A flow diagram is shown in Fig.4. Where ‘sync word’ is used, this implies both the standard POCSAG sync word and any enabled User Programmable Sync Word (UPSW).

Several modes of operation can be distinguished depending on the synchronization state. Each mode uses a different method to obtain or retain data synchronization. The receiver and oscillator enable outputs (RXE and ROE respectively) are switched accordingly, with the appropriate establishment times (t

RXON

and t

ROON

respectively). Before comparing received data with preamble, an

enabled sync word or programmed user addresses, the appropriate error correction is applied.

Initially, after switching to the ON status, the decoder is in switch-on mode. Here the receiver will be enabled for a period up to 3 batches, testing for preamble and the sync word. Failure to detect preamble or the sync word will cause the device to switch to the ‘carrier off’ mode.

When preamble is detected it will cause the device to switch to the preamble receive mode, in which a sync word is searched for. The receiver will remain enabled while preamble is detected. When neither sync word nor preamble is found within a 1 batch duration the ‘carrier off’ mode is entered.

Upon detection of a sync word the data receive mode is entered. The receiver is activated only during enabled user address frames and sync word periods. When an enabled user address has been detected, the receiver will be kept enabled for message code-word reception until the call termination criteria are met.

During call reception data bytes are stored in an internal SRAM buffer, capable of storing 2 batches of message data.

Messages are transmitted contiguously, only interrupted by sync words at the beginning of each batch.

1999 Jan 08 10

Philips Semiconductors Product speciﬁcation

Enhanced Pager Decoder for APOC1/POCSAG

PCD5002A

When a message extends beyond the end of a batch no testing for sync takes place. Instead, a message data transfer will be initiated by an interrupt to the external controller. Data reception continues normally after a period corresponding to the sync word duration.

If any message code-word is found to be uncorrectable, the ‘data fail’ mode is entered and no data transfer will be attempted at the next sync word position. Instead, a test for sync word will be carried out.

In the data fail mode message reception continues normally for 1 batch duration. When a sync word is detected at the expected position the decoder returns to the ‘data receive’ mode. If the sync word again fails to appear, then batch synchronization is deemed lost. Call reception is then terminated and the ‘fade recovery’ mode is entered.

Thefade recovery mode is intended to scan for sync word and preamble over an extended window (nominal position ± 8 bits). This is performed for a period of up to

15 batches, allowing recovery of synchronization from long fades in the radio signal. Detection of preamble causes switching to the ‘preamble receive’ mode, while sync word detection causes switching to the ‘data receive’ mode. When neither is found within a period of 15 batches, the radio signal is considered lost and the ‘carrier off’ mode is entered.

The purpose of the carrier off mode is to detect a valid radio transmission and synchronize to it quickly and efficiently. Because transmissions may start at random, the decoder enables the receiver for 1 code-word in every 18 code-words looking for preamble or sync word. By using a buffer containing 32 bits (n bits from the current scan, 32 − n from the previous scan) effectively every batch bit position can be tested within a continuous transmission of at least 18 batches. Detection of preamble causes the device to switch to the ‘preamble receive’ mode, while sync word detection causes the device to switch to the ‘data receive’ mode.

Fig.4 ACCESS synchronization algorithm for POCSAG.

handbook, full pagewidth

OFF to ON status

preamble

sync word

no sync wordsync word

preamble

preamblesync word

no preamble or sync word

(3 batches)

no preamble or sync word

no preamble or sync word (1 batch)

no preamble or sync word (15 batches)

switch-on

preamble receive

data receive

data fail

fade recovery

carrier off

(1 batch)

MLC247

1999 Jan 08 11

Philips Semiconductors Product speciﬁcation

Enhanced Pager Decoder for APOC1/POCSAG

PCD5002A

Fig.5 APOC1 synchronization algorithm.

handbook, full pagewidth

batch zero identify

no batch zero ID

batch zero ID

TX off time out

no sync word or preamble

no sync word

sync word

OFF to ON status

preamble

sync word

no preamble (1 batch)

no preamble

or sync word

(3 batches)

short fade recovery

transmitter off

preamble receive 2

sync word

sync

word

no sync word

TX off time out

preamble

no preamble

(1 batch)

MGD269

batch zero detect

preamble receive 1

long fade recovery

carrier detectswitch on

preamble

cycle receive

8.14 APOC1 synchronization strategy

The synchronization strategy in APOC1 is an extended version of the ACCESS scheme and is illustrated in Fig.5. The PCD5002A counts the number of batches in a transmission, starting from the first batch received after preamble. Counter overflow occurs due to the size of a cycle, as determined by SPF programming.

Initially, after switching to the ON status, the decoder will be in the switch-on mode. Here the receiver will be enabled for up to 3 batches, testing for preamble and sync word. Detection of preamble causes the device to switch to the ‘preamble receive’ mode, while any enabled sync word enters the ‘batch zero detect’ mode. Failure to detect either will cause the device to switch to the ‘carrier detect’ mode.

In thepreamble receive 1 mode the PCD5002A searches for a sync word, the receiver remaining enabled while preamble is detected. As soon as an enabled sync word is found the ‘batch zero identify’ mode is started.

If preamble is not found within one batch duration then the ‘long fade recovery’ mode is entered.

When in batch zero detect mode the PCD5002A switches on every batch to maintain synchronization and check for the batch zero identifier. Detection of the batch zero identifier activates the ‘cycle receive’ mode. When synchronization is lost the ‘long fade recovery’ mode is entered. ‘preamble receive’ mode is entered when preamble is detected.

In the batch zero identify mode the first code-word immediately after the sync word of the first batch is compared with the programmed batch zero identifier. Failure to detect the batch zero identifier will cause the device to enter the ‘short fade recovery’ mode.

When this comparison is successful the function bits determine whether any broadcast message will follow. Any function bit combination other than ‘1,1’ will cause the PCD5002A to accept message code-words until terminated by a valid address code-word.

1999 Jan 08 12

Philips Semiconductors Product speciﬁcation

Enhanced Pager Decoder for APOC1/POCSAG

PCD5002A

After reception of any broadcast message data the PCD5002A continues to operate in the ‘cycle receive’ mode.

In the cycle receive mode the PCD5002A enables call reception in only one programmed batch per cycle. Sync word detection takes place from 2 bits before to 2 bits after the expected sync word position of this batch. If the sync word is not detected then the position of the current sync word will be maintained and the ‘short fade recovery’ mode will be entered.

When a valid sync word is found user address code-word detection takes place, as in normal POCSAG code. Any following message code-words are received normally. If a message extends into a subsequent batch containing a batch zero identifier, then the batch zero identifier is detected normally and message reception will continue.

Data reception is suspended after the programmed batch until the same batch position in the next cycle. The exception being when a received call continues into the next batch.

In the short fade recovery mode the programmed data receive batch will continue to be checked for user address code-words. In addition the first code-word after the programmed batch is checked for sync word or preamble.

When a valid sync word is detected the ‘cycle receive’ mode is re-entered, while detection of preamble causes the device to switch to the ‘preamble receive’ mode. When neither is found then the ‘transmitter off’ mode is entered.

In the transmitter off mode a time-out is set to a pre-programmed duration. This time-out corresponds to the maximum time between subsequent transmissions (preamble to preamble).

The PCD5002A then checks the first batch of every cycle for sync word or preamble. The programmed data receive batch is ignored (unless it is batch 0).

Table 4 Synchronization window tolerance as a function

of bit rate

TIME FROM LOSS

OF SIGNAL

TOLERANCE

512

(bits/s)

1200

(bits/s)

2400

(bits/s)

≤30 s 4 bits 4 bits 4 bits

≤60 s 4 bits 4 bits 8 bits ≤120 s 4 bits 8 bits 16 bits ≤240 s 8 bits 16 bits 32 bits

Synchronization checking is performed over a window ranging from ‘n’ bits before to ‘n’ bits after the expected sync word position. The window tolerance ‘n’ depends on the time since the ‘transmitter off’ mode was entered and on the selected bit rate (see Table 4).

When a sync word is detected in this widened synchronization window the PCD5002A enters the ‘batch zero identify’ mode. Time-out expiry before a sync word has been detected causes the device to switch to the ‘long fade recovery’ mode.

Detection of preamble in the ‘transmitter off’ mode initiates the preamble receive 2 mode. Operation in this mode is identical to ‘preamble receive mode’. Failure to detect preamble for one batch period will cause the device to switch back to the ‘transmitter off’ mode. This prevents inadvertent loss of cycle synchronization due to spurious signals resembling preamble.

The carrier detect mode is identical to the ‘carrier off’ mode in standard POCSAG operation. Upon first entry the transmitter off time-out is started. The receiver is enabled to receive one code-word in every 18 code-words to check for sync word and preamble. This check is performed on the last available 32 bits for every received bit.

The ‘preamble receive’ mode is entered if preamble is detected. If a valid sync word is found the ‘batch zero detect’ mode is entered. If neither has been detected and the time-out expires, then the ‘long fade recovery’ mode is entered.

The long fade recovery mode is intended to quickly regain synchronization in fading conditions (not caused by the transmitter switching off between transmissions) or when having been out of range, while maintaining acceptable battery economy.

Initially, the receiver is switched off until one cycle duration after the last enabling in the ‘transmitter off’ mode. The receiver is then enabled for a 2 code-word period in which each contiguous group of 32 bits is tested for any decodable POCSAG code-word (including sync word) and preamble. Single-bit error correction is applied.

If a code-word is detected, the receiver enable period is extended by another code-word duration and the above test is repeated. This process continues while valid code-words are received.

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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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Philips Semiconductors Product speciﬁcation

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PCD5002A

Table 5 Call header format

Table 6 Call header bit identiﬁcation

Note

1. The DF bit in the call header is set: a) When the sync word of the batch in which the (beginning of the) call was received, did not match the standard

POCSAG or a user-programmed sync word. The sync word identifier (bits S3 to S1) will then be made 0.

b) When any code-word of a previous call received in the same batch was uncorrectable.

Table 7 Message data format

Table 8 Message data bit identiﬁcation

Table 9 Call terminator format

BYTE NUMBER

BIT 7

(MSB)

BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1

BIT 0

(LSB)

1 0 S3 S2 S1 R3 R2 R1 DF 2 0 S3 S2 S1 R3 R2 R1 0 3 X X F0F1E3E2E1 0

BITS (MSB TO LSB) IDENTIFICATION

S3 to S1 identiﬁer number of sync word for current batch (7 = standard POCSAG) R3 to R1 identifier number of user address (RIC)

DF data fail mode indication (1 = data fail mode); note 1

F0 and F1 function bits of received address code-word (bits 20 and 21)

E3 to E1 detected error type; see Table 11; E3 = 0 in a concatenated call header

BYTE NUMBER

BIT 7

(MSB)

BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1

BIT 0

(LSB)

1 M2M3M4M5M6M7M8M9 2 M10 M11 M12 M13 M14 M15 M16 M17 3 M18 M19 M20 M21 E3 E2 E1 M1

BITS (MSB TO LSB) IDENTIFICATION

M2 to M21 message code-word data bits

E3 to E1 detected error type; see Table 11

M1 message code-word flag

BYTE NUMBER

BIT 7

(MSB)

BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1

BIT 0

(LSB)

1 FTS3S2S1 0 0 0 DF 2 FTS3S2S1 0 0 0 X 3 XXXXE3E2E10

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Philips Semiconductors Product speciﬁcation

Enhanced Pager Decoder for APOC1/POCSAG

PCD5002A

Table 10 Call terminator bit identiﬁcation

Note

1. The DF bit in the call terminator is set: a) When any call data code-word in the terminating batch was uncorrectable, while in ‘data receive’ mode. b) When the sync word at the start of the terminating batch did not match the standard POCSAG or a

user-programmed sync word, while in ‘data fail’ mode.

Table 11 Error type identiﬁcation (note 1)

Note

1. POCSAG code allows a maximum of three bit errors to be detected per code-word.

BITS (MSB TO LSB) IDENTIFICATION

FT forced call termination (1 = yes)

S3 to S1 identifier number of last sync word

DF data fail mode indication (1 = data fail mode); note 1

E3 to E1 detected error type; see Table 11; E3 = 0 in a call terminator

E3 E2 E1

ERROR TYPE

NUMBER OF ERRORS

0 0 0 no errors; correct code-word 0 0 0 1 parity bit in error 1 0 1 0 single bit error 1 + parity 0 1 1 single bit error and parity error 1 1 0 0 not used − 1 0 1 4-bit burst error and parity error 3 (e.g. 1101) 1 1 0 2-bit random error 2 1 1 1 uncorrectable code-word 3 or more

8.18 Error type indication

Table 11 shows how the different types of detected errors are encoded in the call data output format.

8.19 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 code-word.

When the PCD5002A 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 I

C-bus interface. Bytes will be output starting from the position indicated by the RAM read pointer.

Call termination can occur on reception of an address code-word (or even a message code-word if in Enhanced Call Termination Mode) or when a sync word is not

detected while in the ‘Data Fail’ mode (‘Short Fade Recovery’ in APOC1).

8.20 Continuous data decoding

Apart from transmissions in the POCSAG or APOC1 format, the PCD5002A is also capable of decoding continuous transmissions with the same code-word structure. Any User-Programmable Sync Word (UPSW) may be designated to enable continuous data decoding.

When a Continuous Data Decoding (CDD) sync word is detected at any sync word position, the receiver remains enabled from then on. Status bits D1 and D0 show the CDD mode to be active.

All code-words are decoded and their data fields are stored in SRAM. The usual error information is appended. No distinction is made between address and message code-words: code-word bit 0 is treated as a data bit and is stored in bit M1 of the 3-byte output format.

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