JPH07322329A - Selective calling receiver with battery-saving function and its method - Google Patents

Abstract

PURPOSE: To extend the life of a battery by shortening the feeding time of the selective call receiver. CONSTITUTION: The selective call receiver 200 includes a receiver 204 for receiving a paging signal. A detector connected to a baud rate detector 224 included in a synchronization acquiring circuit detects a synchronizing code word. In accordance with the detection of the synchronizing code word, address information is decoded. A synchronization maintaining circuit includes a circuit for maintaining synchronization with the paging signal during the period of address decoding and enabling a power supply controller 210. The detector 224 detects a baud rate at least for a period between the 1st and 2nd parts of addresses in accordance with the power supply to the receiver 200. A preamble detector detects a preamble at least for a part of the 2nd address in accordance with the reception of the 2nd part of the addresses.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to a selective call receiver, and more particularly to a selective call receiver having a battery saving function and a method thereof.

[0002]

BACKGROUND OF THE INVENTION With the demand for reduced size and portability and convenience of selective call receivers, selective call receivers rely primarily on battery power supplies powered by batteries of limited energy content. There is. Therefore, users desire power saving methods in selective call receivers that improve battery life. One of the main current consuming circuits in the selective call receiver is the receiver circuit. The receiver circuit must be energized so that the selective call receiver can receive radio signals intended to be received by the selective call receiver, but the receiver circuit is It can be de-energized during other operations of the selective call receiver.

One example of a conventional power saving method involves determining whether a carrier frequency indicates that a transmission intended for a radio receiver is being received. While it is possible to quickly determine whether a carrier frequency is being received, a wireless system can transmit many types of information on the carrier frequency, some of which are destined for the selective call receiver. This can unnecessarily drain battery power to a receiver that is unaware of this.

The selective call receiver activates the receiver circuitry only during the preamble portion of the received signaling protocol and only during the address portion of the received selective call message to cause the message to reach the selective call receiver. Battery life can be improved by determining whether or not it is intended.

[0005]

However, a typical battery saving method is for each received address to perform address correlation to quickly determine whether the address is that of its selective call receiver. It needs to be activated during the reception of a sufficient portion of the address. Moreover, typical battery saving methods require the selective call receiver to know when an address is received within the signaling protocol. For example, the conventional battery saving method is a Post Office Code.
Standardization Advisory
It is possible to take advantage of the fact that there is frame allocation and address generation in place within the Group (POCSAG) signaling protocol. Also, prior to detecting its address, the selective call receiver must detect a sync codeword that enables the selective call receiver to achieve word synchronization.

Accordingly, it is an object of the present invention to provide a battery saving method that saves power by energizing a receiver circuit for a period shorter than conventional detection periods for preamble detection, address correlation and sync codeword detection. Is to provide.

[0007]

A selective call receiver comprises means for receiving a paging signal that includes a preamble, a sync codeword, and at least address information. The selective call receiver further includes means for controlling the power supply to the receiving means for receiving the paging signal, and is coupled to the receiving means for obtaining synchronization for the paging signal. Means are provided. The synchronization acquisition means comprises means for detecting a baud rate and means for detecting a sync codeword coupled to the means for detecting the baud rate. The selective call receiver further comprises means for decoding the address information in response to the synchronization codeword being detected, and for maintaining synchronization to the paging signal during address decoding. It is equipped with means. The synchronization maintaining means comprises means for selectively enabling the power supply control means for receiving a paging signal. The baud rate detecting means detects a baud rate during at least first and second portions of the address in response to power being supplied to the receiving means. The selective call receiver further comprises means for detecting a preamble during at least a portion of the second address in response to receiving the second portion of the address.

According to the present invention, there is further provided a method for reducing power consumption in a power consuming selective call receiver, the method comprising: (a) a preamble, a synchronization codeword, and at least address information. Receiving a paging signal including: (b) controlling the supply of power to a receiving means for receiving the paging signal; (c) obtaining synchronization with the paging signal, the synchronization The obtaining step comprises: (d) detecting a baud rate; and (e) detecting the sync codeword; (f) decoding address information in response to the step (c). (G) maintaining synchronization with a paging signal during decoding of the address, the step of maintaining the synchronization includes (h) the paging signal. Selectively enabling the power supply control means for receiving, (i) detecting a baud rate between at least first and second portions of the address, and (j) at least a second. Detecting the preamble between a part of the addresses.

[0009]

EXAMPLES Referring to FIG. 1, the traditional Post Of
fine Code Standardization
A signaling diagram showing the signaling of the Advisory Group (POCSAG) protocol includes a series of addresses and / or message information directed to individual selective call receivers or groups of selective call receivers assigned to the paging system. These series of addresses are assembled on demand and transmitted as a continuous transmission signal. The transmission is in digital format and is equal to the duration of one batch and one additional codeword, at least 5
Starting with a 76-bit preamble 102. The preamble 102 is followed by one or more batches of addresses and message codewords. Each batch begins with a sync codeword (SC) 104, followed by eight frames 106, each frame 106 having a duration equivalent to two codewords 108, 110, an address codeword and / or a message codeword. Have.

As shown in FIG. 2, the timing diagram according to the present invention shows that the selective call receiver searches the received signal for the sync word (SC) 104 at least once after the detection of the preamble 102. . However, thereafter, the sync codeword 104 need not be decoded within each batch before decoding the received address words 150, 152, at least when the selective call receiver is synchronous to the POCSAG protocol signal or otherwise. Only the baud rate of the received information needs to be detected while the address is being decoded to determine if it is in sync with the protocol signal. This is shown in the latter part of FIG. 2, where the first and second addresses 15 will be described further below.
The timing requirements for decoding at least the first and second parts of 0,152 are shown.

FIG. 3 is an electrical block diagram of paging system 150 showing a paging transmitter and selective call receiver according to a preferred embodiment of the present invention. The paging transmitter is coupled to an input device, eg, telephone 256, to enter a message or initiate a page via paging controller 254. The paging controller 254 is, inter alia, the respective selective call receiver 2 according to the POCSAG signaling protocol, for example.
Generate a page to be sent to 00. The paging controller 254 is coupled to a radio frequency transmitter / receiver 252, the radio frequency transmitter / receiver 252 being an antenna 2
Send the page via 50. Receiving, processing and sending selective call messages are well known to those skilled in the art.

The page is received by the selective call receiver 200. The selective call receiver 200 is a receiver 2
An antenna 202 is provided for capturing a transmitted radio frequency (RF) signal that is coupled to the input of 04. The RF signal is preferably a selective call (paging) message signal that provides the address of the receiver and associated message, such as a numeric or alphanumeric message. However, it is understood that other well known paging signal formats, such as tone only signals or tone and voice signals, can be used as well. Receiver 204 processes the RF signal and produces at its output a data stream representing the demodulated data information. The demodulated data information is coupled to the input of decoder / controller 206, which processes the information in a manner well known in the art. Coupled to the controller 206,
The baud detector 224 is used to detect the baud rate of the received paging signal. The power switch 210, coupled to the decoder / controller 206, is the receiver 2
Controls the supply of power to 04, thereby providing a battery saving function, which is described in more detail below.

For the purposes of explanation, other signal formats may of course be used as well, but are well known in the art.
Assume that the CSAG signal format is used. When an address is received by the decoder / controller 206, the received address is compared to one or more addresses stored in the code plug (or code memory) 222, and if a match is detected, the user On selective call message, or page,
An alert signal is generated to alert that a has been received. The alarm signal is directed to an audible alarm device 214 to generate an audible alarm or to a tactile alarm device 216 to generate a quiet vibration alarm. Switch 2
20 enables the user of the selective call receiver to select, among other things, between the audible alert device 214 and the tactile alert 216 in a manner well known in the art.

The subsequently received message information is stored in memory 304 (FIG. 4) and can be accessed for display by a user using one or more of said switches 220, said switches 220. Provides additional functionality such as reset, read, and delete. In particular, by using the appropriate functionality provided by switch 220, the stored message is read from memory and the display 208 allows the user to view the message.
Decoder / Controller 206 for display by
Processed by.

The controller / decoder 206 of FIG. 3 can be implemented using a microcomputer as shown in FIG. FIG. 4 is an electrical block diagram of a microcomputer-based decoder / controller suitable for use in the selective call receiver of FIG. As shown, the microcomputer 206 is preferably a MC68HC05 type microcomputer, such as that manufactured by Motorola, Inc., which includes an on-board display driver 314. The microcomputer 206
Includes an oscillator 318 that generates the timing signals used in the operation of the microcomputer 206. A crystal, or crystal oscillator (not shown), is coupled to the input of oscillator 318 and provides a reference signal for establishing the timing of the microcomputer. Timer / counter 3
02 is coupled to oscillator 318 and provides a programmable timing function used in controlling the operation of the receiver or processor.

RAM (Random Access Memory) 304
Are used to store variables obtained during processing as well as to enable storage of message information received during operation as a selective call receiver. A ROM (Read Only Memory) 306 stores a subroutine for controlling the operation of a receiver or a processor which will be described later. In many microcomputer configurations, the programmable ROM (PROM) memory area can be provided by programmable read only memory (PROM) or EEPROM (electrically erasable programmable read only memory). The oscillator 318, timer / counter 302, RAM 304, and ROM 306 are coupled to a central processing unit (CPU) 310 via an address / data / control bus 308 and the central processing unit (C)
PU) 310 executes instructions and controls the operation of microcomputer 206.

Demodulated data generated by the receiver is coupled to microcomputer 206 via input / output (I / O) port 312. The demodulated data is the CPU
If the received address is the same as that processed by 310 and stored in, for example, a code plug memory coupled to the microcomputer via I / O port 313, then the message, if any, is received. It is also stored in the RAM 304. The reading of the stored message and the selection of the predetermined destination address are
This is done by a switch coupled to O port 312.
The microcomputer 206 then reads the stored message and directs the information via the data bus 308 to the display driver 314, which processes the information and LCs the information.
Formatting for presentation by a display 208 (FIG. 3) such as D (Liquid Crystal Display).
The alert signal is generated when the address of the selective call receiver is received, and the alert signal can be routed to the alert generator 316 via the data bus 308, which is described above. An alarm enable signal is provided to the audible alarm device. Alternatively, as mentioned above, if the vibration alarm is selected, the microcomputer is coupled to the I / O port 313 via the data bus 308 to allow the generation of a vibration or silent alarm. Generates an alarm enable signal.

The power saving switch 2 is used for battery saving operation.
Data bus 3 to I / O port 312 coupled to 10
Controlled by CPU 310 using a battery saving signal routed through 08. Power is periodically applied to the receiver to enable decoding of the received selective call receiver address signal and any message information intended for the receiver or transmitter.

Referring to FIG. 5, there is shown an electrical block diagram of a configuration for decoding the microcomputer shown in FIG. As mentioned above, the ROM stores subroutines for controlling the operation of the selective call receiver. However, those skilled in the art will understand that the operation of the selective call receiver can also be controlled by hardware circuitry. In accordance with the preferred embodiment of the present invention, the selective call receiver 200 includes a baud detection circuit 224.
The baud rate of the received signal is detected by (FIG. 3). If a valid baud rate is detected, the selective call receiver 200 uses the preamble detector (or preamble detector) 404 to obtain the POC to obtain bit synchronization.
Search SAG signaling protocol for preamble.
A sync codeword detector (sync detector) 406 searches the sync codeword (SC) to determine word sync in a manner well known to those skilled in the art. If a preamble and sync codeword are detected, the selective call receiver examines its assigned frame to attempt to locate its assigned address. Also, if the assigned frame is not the next frame, the timing and control block 412 sends a signal to the power switch 210, which switches the receiver of the selective call receiver 200 until the assigned frame arrives. Turn off power to 204. In the assigned frame, the address decoder 408 detects at least the first 8 bits of the correlated first address word 150, and if the correlation matches, the rest of the address is decoded and received. It is determined if the address matches the assigned address within at least 2 bits of the error. During the first 8-bit address decoding, a baud rate detector (baud detector) 224 (FIG. 3) also detects the baud rate of the received signal and the received signal is a valid baud rate, or Determine if it is an invalid baud rate.
If the address is not recognized during the first 8 bits of the first address, the receiver turns off until the arrival of the second address in the assigned frame. When the second address is received, baud rate and preamble detection is likewise performed during the first 8 bits of the second address. The receiver can either (1) match the address within a 2-bit error, (2) match the preamble within a 1-bit error, or (3) match the two of the first and second addresses. 16 including 8 bits
It remains on only for 8 bits, unless baud rate detection is done over the bit time interval. However, if the baud rate is not detected only in the 8 bits of the second address, the failure is noted by the microcomputer.

Further, when any of the above three conditions are met, the receiver remains on for an additional 8-bit time interval. If any of the three conditions are valid during the additional 8-bit time interval, the receiver will receive 32 of the second address.
It stays on until the bits are correlated. Also, during address correlation, (1) if the address matches within a 2-bit error, or (2) if a valid baud rate is detected and no preamble is detected, the receiver will use normal POCSAG decoding. It will remain in the characterized synchronous operating mode. However,
If the preamble is detected within a 2-bit error for a 32-bit address word and a valid baud is detected, or (2) if the invalid baud rate is 5
If detected for 6 bits, the receiver exits synchronous mode and begins decoding the preamble asynchronously.

In this way, the receiver maintains synchronization with the received signal by decoding the address information, and the receiver has some recognition during the first 8 bits of the first address. If no address bit is detected, the receiver will conserve battery until it is time to receive the second address. During this time, the receiver can determine whether valid information is received, and if valid information is received, it continues to operate in synchronous mode, and if not, the receiver Proceeds to search for the preamble and sync codeword in asynchronous mode under the assumption that has lost synchronization with the received signal or has not received a valid signal. The receiver thus preferably utilizes the address or data word to achieve synchronization by detecting the baud rate information. The receiver also searches for a preamble if the address is not decoded in the first address codeword and the receiver now receives the preamble information because it lost synchronization with the previous signal. Be able to quickly determine whether or not Therefore, the receiver improves battery saving, whether the receiver loses synchronization by determining whether a preamble is detected during the time allotted to the second address codeword. This is because it can be quickly decided.

Further, while the selective call receiver increases battery life by improving the battery saving function, the selective call receiver has two invalid baud rate detection times 16 bits (ie, the first and second 2 first 8 bits of the second 8 bit address)
Increase the "on time" of the receiver if detected. However, this increase in receiver "on-time" is effective for 8 bits at a time, which does not significantly impact battery life, and to optimize battery life while minimizing errors at the receiver. Will bring an extremely robust method of.

Referring to the flow chart of FIG. 6, the preferred operation of the selective call receiver is illustrated. The selective call receiver powers up and initializes all variables in step 500. The baud detection circuit initiates detection of received information to detect that a valid baud rate is being received, step 502. In step 504, the baud rate is checked to determine if a valid or invalid baud rate has been received. If an invalid baud rate is detected, the receiver is turned off by the power switch 210, step 506. Alternatively,
If a valid baud rate is detected in step 504, the preamble detector looks up the received data in step 508 for a preamble. Step 510 determines whether a preamble has been detected. If no preamble is detected, step 51
At 4, the timeout routine is entered. If the timeout period has not expired, the search for preambles continues at step 508. However, if the timeout period has elapsed, then in step 506 the receiver is turned off. Alternatively, step 51
At 0, if the preamble is detected, the sync detector initiates detection of the sync codeword, step 51.
6. Step 518 detects if a sync codeword has been received. If not, the receiver continues the search for a sync codeword in step 516. Alternatively, in step 518, if a sync codeword is detected, and if possible,
The receiver turns off and waits for the arrival of its assigned frame, step 520. When the assigned frame is reached, the receiver powers up to receive the assigned frame, and the baud detection circuit searches for a valid baud rate during the first 8 bits of the first address. , Step 522.
If in step 524 the first 8 bits of the first address do not match the address stored in the code plug, then baud rate detection is aborted in step 528. The receiver circuit, in step 530,
To continue baud rate detection, it is turned off until the arrival of the first 8 bits of the second address (ie, the first 8 bits of the second codeword of the frame).

The flowchart of FIG. 6 continues from FIG. 7, which further illustrates the operation of the selective call receiver of FIG. In step 532, the receiver turns on and enables the baud rate circuit and preamble detector. In step 534, the first 8 bits of the second address are correlated, and in step 534, if the address is detected, preferably within a 2-bit error, then the next 8 bits of the address part are Retrieved and correlated, step 526. However, if the addresses do not match, the receiver checks in step 536 if a preamble has been detected. If so, the receiver proceeds to step 52.
Then, in 6, the 8-bit address is decoded. Alternatively, if the preamble has not been detected, then in step 538, the baud rate detector determines whether a valid baud rate is being received. If so, the receiver turns off and waits for the next frame in the next batch of information, step 544. However, if an invalid baud rate is detected in step 538, then the receiver determines in step 540 whether this is a second detection of an invalid baud rate (eg, flag for invalid baud rate is set. Check). If it is a second detection of an invalid baud rate, the receiver resets the invalid baud rate flag and begins decoding the next 8-bit address, step 526. However, if this is the first occurrence of an invalid baud rate detection, the receiver sets the invalid baud rate detection flag in step 542, and then in step 544 its assigned frame in the next batch. Turn off until the arrival of.

Alternatively, if in steps 524 and 534 the first 8-bit address is received (the first address codeword in step 524, or the second address codeword in step 534), then the address decoder causes step 526 At, the decoding of the next (eg, second) 8-bit information is started and at step 546 it is determined that address correlation has occurred at some of the valid addresses. If no address is found, step 548.
At, preamble detection is started. If no preamble is detected, step 550 checks to see if a valid baud rate has been detected, and if so, the receiver turns off and waits for its assigned frame in the next batch of information. 5
44. However, if the address is decoded in step 546, or the preamble is detected in step 548, or, finally, an invalid baud rate is detected in step 550, the receiver determines in step 552 the address. Start decoding the rest of the. In step 554, the receiver determines if the address matches that stored in memory, and if so, step 556 determines if a preamble is detected and if it is detected. If so, finally, in step 558, the receiver determines whether a valid baud rate is detected, and if a valid baud rate is detected, the receiver operates in synchronous mode in step 560. To continue. In the synchronous mode of operation, the receiver continues to detect its assigned frame in the received information for each batch, and during address decoding, as mentioned above, the receiver obtains the synchronous information, and thus You do not need to turn on to receive any other sync codeword. However, if no address match is detected in step 554, or a preamble is detected in step 556, or an invalid baud rate is detected, the receiver suspends its synchronous mode of operation in step 562. And the operation of asynchronous mode is started. In asynchronous mode of operation, the receiver initiates a search of the received information for a preamble and a sync codeword, which causes the receiver to
This is because it is assumed at this point that it has lost synchronization with the received signal or has not received a transmission from the base site transmitter.

In this way, the receiver maintains synchronization by decoding the address information, and if the receiver does not detect a recognizable address bit during the first 8 bits of the first address. In addition, the receiver performs battery saving until it receives the second address.
During this time, the receiver can determine if valid information has been received, and if so, it will continue to operate in its synchronous mode, otherwise the receiver will receive. Proceed to detect the preamble and subsequent sync codewords in asynchronous mode under the assumption that the signal has lost sync or has not received a valid signal. The receiver thus detects the address and / or to achieve synchronization by detecting the baud rate information.
Or use the data word. The receiver also searches for a preamble if the address is not decoded for the first address and quickly determines if the receiver is now receiving preamble information because the receiver has lost synchronization with the previous signal. It can be so. Therefore, the receiver can improve battery saving, which quickly determines whether synchronization is lost by determining if a preamble was detected during the second address codeword. Because you can.

In summary, there is provided a selective call receiver comprising means for receiving a preamble, a sync codeword, and at least a paging signal containing address information. The selective call receiver further comprises means for controlling the supply of power to the receiving means for receiving a paging signal. The selective call receiver further comprises:
There is a means coupled to the control means for disabling power to the receiving means, and a means coupled to the receiving means for obtaining synchronization to the paging signal.
The means for obtaining synchronization comprises means for detecting valid and invalid baud rates, and means for detecting sync codewords coupled to the baud rate detecting means. The selective call receiver further comprises means for decoding address information in response to the sync codeword being detected. The selective call receiver further includes means for maintaining synchronization to a paging signal during the address decoding. The synchronization maintaining means comprises means for selectively enabling the power supply control means to receive a paging signal. The baud rate detecting means is responsive to at least power supply to the receiving means to supply at least first and second addresses.
The baud rate is detected during the part. A means is responsive to the second part of the address being received,
A preamble is detected during at least a part of the second address. Also, the means coupled to the receiving means starts the reception in the asynchronous mode and the baud rate detecting means starts the reception in the synchronous mode in response to detecting two invalid baud rates.

[0028]

As described above, according to the present invention, in the selective call receiver, the receiver circuit is turned on for a period shorter than the conventional detection period for preamble detection, address correlation and sync codeword detection. By doing so, it is possible to operate properly, and thus it is possible to reduce power consumption and extend battery life more than ever before.

[Brief description of drawings]

FIG. 1 is a signal format diagram showing signals of a conventional POCSAG protocol.

FIG. 2 is a timing diagram showing an address detection mechanism according to a preferred embodiment of the present invention.

FIG. 3 is an electrical block diagram of a paging system showing a paging transmitter and selective call receiver according to a preferred embodiment of the present invention.

4 is an electrical block diagram of a microcomputer used in the selective call receiver of FIG.

5 is an electrical block diagram showing a configuration for decoding of the microcomputer shown in FIG.

FIG. 6 is a flow chart illustrating operation of the selective call receiver of FIG.

7 is a flowchart showing the operation of the selective call receiver of FIG. 3 subsequent to FIG. 6;

[Explanation of symbols]

 102 preamble 104 synchronization word 106 frame 108, 110 code word 150, 152 address word 200 selective call receiver 202 antenna 204 receiver 206 decoder / controller 208 display 210 power switch 214 audible alarm 216 tactile alarm 220 switch 222 cord plug 224 baud detection 250 antenna 252 radio frequency transmitter / receiver 254 paging controller 256 telephone 302 timer counter 304 RAM 306 ROM 308 data bus 310 central processing unit 312, 313 I / O port 314 display driver 316 alarm generator 318 oscillator 404 preamble detector 406 synchronization detection unit 408 address decoder 410 data detection unit 412 data Imming and control

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Lenny Zureta, Jackson Road, Delray Beach, Florida 33484, United States 15373 (72) Inventor David Jay Hayes Florida 33324, Plantation, Northwest Force・ Street 10563

Claims (8)

[Claims] 1. A selective call receiver, means for receiving a paging signal comprising a preamble, a sync codeword, and at least address information, providing power to said receiving means for receiving said paging signal. Means for controlling the baud rate, means for controlling synchronization with the receiving means, means for obtaining synchronization to the paging signal, means for detecting a baud rate, and means for detecting the baud rate. Means for detecting the synchronization codeword, means for decoding the address information in response to the detection of the synchronization codeword, and means for decoding the address information during the address decoding. Means for maintaining synchronization with a paging signal, said synchronization maintaining means comprising: Means for selectively enabling the power supply control means to receive a signal, between at least first and second portions of the address in response to power being applied to the receiving means Said synchronization maintaining means comprising: said baud rate detecting means for detecting a baud rate; and means for detecting a preamble during at least a portion of said second address in response to a second portion of said address being received. A selective call receiver, comprising: 2. The selective call receiver of claim 1, further comprising disable means for disabling power to the receiving means when an invalid baud rate is detected. 3. The preamble detection means further comprises start means for starting an asynchronous reception mode of the reception means in response to decoding the preamble at the second address. The selective call receiver according to claim 1. 4. The selective call receiver according to claim 3, wherein the starting means starts the synchronous reception mode of the receiving means in response to the synchronization acquisition means synchronizing with the paging signal. 5. A method for reducing power consumption in a power consuming selective call receiver comprising: (a) receiving a paging signal including a preamble, a sync codeword, and at least address information; (b) said Controlling the supply of power to the receiving means for receiving a paging signal, (c) acquiring synchronization with the paging signal, (d) detecting a baud rate, and (e) Detecting the synchronization codeword; acquiring the synchronization; and (f) decoding address information according to the step (c), (g) maintaining synchronization with the paging signal during the decoding of the address. (H) selectively enabling the power supply control means to receive the paging signal Synchronization maintenance comprising: (i) detecting a baud rate during at least first and second portions of the address; and (j) detecting a preamble during at least a portion of the second address. A method of reducing power consumption in a power consuming selective call receiver, comprising: 6. The method of claim 5, wherein the step of acquiring synchronization acquires synchronization in response to step (e) detecting two invalid sync codewords. 7. The method of claim 5, further comprising the step of initiating receiving a paging signal in synchronous and asynchronous modes in response to the baud rate detecting step. 8. A selective call receiver, means for receiving a paging signal comprising a preamble, a sync codeword, and at least address information, powering said receiving means for receiving said paging signal. Means for controlling power to said receiving means coupled to said control means, means for obtaining synchronization with said paging signal, coupled to said receiving means, Means for detecting bad and invalid baud rates,
And the synchronization acquisition means, which is coupled to the baud rate detection means, for detecting a synchronization codeword, and means for decoding the address information in response to the detection of the synchronization codeword. Means for maintaining synchronization with the paging signal during the address decoding, means for selectively enabling the power supply control means to enable reception of the paging signal, The baud rate detecting means for detecting a baud rate during at least a first and a second portion of the receiving address in response to power being supplied to the receiving means; and a second portion of the address received. Depending on
Means for detecting a preamble during at least a portion of the second address, coupled to the synchronization maintaining means, and the receiving means, in response to the baud rate detecting means detecting two invalid baud rates. Means for initiating asynchronous mode reception and synchronous mode reception by means of a selective call receiver.