WO2002031671A2

WO2002031671A2 - Communication between a computer and a modem

Info

Publication number: WO2002031671A2
Application number: PCT/US2001/042549
Authority: WO
Inventors: Rich Karstens; Regis Nicolas; Herve Fayolle; Denis Berger; Michel Bonansea; Yann Cheri
Original assignee: Palm, Inc.
Priority date: 2000-10-13
Filing date: 2001-10-09
Publication date: 2002-04-18
Also published as: AU2001297006A1; WO2002031671A9; WO2002031671A3

Abstract

A method and system for allowing a host processor and a modem to communicate both data and commands by multiplexing the information. In one embodiment, a connection between the computer system and the modem is established via a communication link. This step may further comprise opening a data channel and a command channel between the two devices. Next, data is encapsulated in a data frame with an indicator in the data frame that it comprises data. Then, a command is encapsulated in a command frame with an indicator that the frame comprises a command. Then, the data frame and the command frame are multiplexed to create a signal. Then, the signal is transferred over the communication link. In another embodiment, the commands are substantially compliant with the Hayes Standard AT Command Set (AT commands). In other embodiments, the computer system may be a portable computer system or a personal digital assistant. In another embodiment, the computer system is a portable electronic device, such as a cell phone, pager, or portable web-bowser.

Description

COMMUNICATION BETWEEN A COMPUTER AND A MODEM

BACKGROUND FIELD The present disclosure relates to the field of data communication,

Specifically, the present disclosure relates to a method and system for a host system and modem to exchange commands and data while in a data mode. In similar specificity, this disclosure reveals a method and a system for serial data multiplexer for continuous communication with modem while in data mode.

RELATED ART

As the components required to build a computer system have reduced in size, new categories of computer systems have emerged. One of the new categories of computer systems is the "palmtop" computer system. A palmtop computer system (otherwise known as a personal digital assistant or PDA) is a computer that is small enough to be held in the hand of a user and can be "palm-sized." Most PDA computer systems are used to implement various Personal Information Management (PIM) applications such as an address book, a daily organizer and electronic notepads, to name a few.

It has proven convenient to transfer data between a PDA and other computer systems. For example, a PDA may send or retrieve electronic-mail; synchronize an address book, a daily organizer, or an electronic notepad; or download software. For example, the PDA may be used to enter sales data into a corporate server. One way for PDAs to communicate with other computer systems is via a modem. The communication between a conventional modem and data terminal (e.g., host processor or PDA) is bi-modal. For example, the modem has a command mode (or command state) for commands and a data mode (or on-line state) for data. In conventional systems, no commands can be transmitted while data are transmitted. Therefore, the on-line state must be terminated to execute commands, for example, commands from the Hayes Standard AT Command Set.

One conventional way to halt the data mode (e.g., on-line state) and enter the command mode (state) is to issue an interrupt or break signal. For example, the string "+ + +" preceded and followed by a one second pause is transmitted to the modem. In this fashion, the data mode (on-line state) is broken and the command mode is entered. However, this is inefficient as relatively long pauses are needed. Additionally, data cannot be transferred between the host and the modem during the command mode. As there may be substantial delays between an issued command and its reply, the communication link between the modem and the host may be idle for substantial periods.

Special situations have arisen making it desirable for a host computer, for example a PDA, to be able to exchange commands with a modem while data are being exchanged. For example, when a modem is transmitting data via radio frequency, it is desirable to display the signal strength on the PDA's display. However, the command mode must be entered to receive signal strength information. In another example, a PDA's user may wish to be notified that electronic-mail has been received via AT commands while the PDA is being used to transmit data. However, this type of electronic-mail notification requires the PDA and modem to be in the command mode. Unfortunately, the notification cannot be received unless the data transmission is halted (e.g., the data mode is left).

Another conventional method allows for multiple data sessions over one serial communication link. This is described in the Technical Specification entitled, "Digital Cellular Telecommunications System (Phase 2+); Terminal

Equipment to Mobile Station (TE-MS) Multiplexer Protocol" (GSM 07.10 version 7.1 .0 release 1998) (ETSI TS 101 369 V7.1.0). However, the methods described in that specification are relatively complex, and hence require a substantial amount of software to execute. Consequently, this conventional method is not suitable for devices which are relatively inexpensive and have somewhat limited memory and processor power, for example PDAs.

SUMMARY OF THE INVENTION

Therefore, it would be advantageous to provide an efficient method and system that allow a host processor to communicate with a modem both data and command information without leaving a data mode. A further need exists for a method and/or system of communicating a substantially full set of AT commands and data while in a single mode. A further need exists for a host processor to receive status from a modem while data is being transmitted between the host and a modem. A still further need exists for such a method and system which is computationally efficient, requires relatively limited software coding, is cost effective, and thus suitable for relatively inexpensive devices with limited processing power and memory, for example, PDAs or portable computers.

Accordingly, the present invention provides an efficient method and system that allow a host processor and a modem to communicate both data and commands by multiplexing the information. Embodiments of the present invention provide for a method and system for communicating a substantially full set of AT commands on one channel multiplexed with data on another channel. AT commands can therefore be communicated validly essentially during data mode. Embodiments of the present invention allow a host processor to receive status from a modem while data is being transmitted between the host and the modem. Embodiments of the present invention provide for such a method and system which is computationally efficient, requires relatively limited coding, is cost effective, and is thus suitable for relatively inexpensive devices with limited processing power and memory, for example, PDAs or portable computers. The present invention provides these advantages and others not specifically mentioned above but described in the sections to follow.

A method and system for allowing a host processor and a modem to communicate both data and commands by multiplexing the information is disclosed. In one embodiment, a connection between the computer system and the modem is established via a communication link. This step may further comprise opening a data channel and a command channel between the two devices. Next, data is encapsulated in a data frame with an indicator in the data frame that it comprises data. Then, a command is encapsulated in a command frame with an indicator that the frame comprises a command. Then, the data frame and the command frame are multiplexed to create a signal. Then, the signal is transferred over the communication link with the data on the data channel and the command on the command channel.

In another embodiment, the commands are substantially compliant with the Hayes Standard AT Command Set (AT commands). In other embodiments, the computer system may be a portable computer system or a personal digital assistant (PDA). In another embodiment, the computer system is a portable electronic device, such as a cell phone, pager, or portable web-browser.

In another embodiment, the signal comprises a first channel comprising data and limited commands and a second channel comprising commands. In one embodiment, the limited commands comprise a reset modem command, a dial telephone command, and a hang-up telephone command. St^' i another embodiment provides for a communication system which comprises a host computer system and a modem connected by a communication link. The host computer system and the modem are operable to communicate over the communication link via a signal comprising multiplexed data and commands. In another embodiment, the host computer system may further comprise a command module which is operable to format a command into a command frame and to indicate in the command frame that the command frame comprises a command. The host also may comprise a data module which is operable to format data into a data frame and to indicate in the data frame that it comprises data. Furthermore, the host may have a multiplexer operable to multiplex the command frames and the data frames.

Still another embodiment provides for a computer readable medium in a computer system having a processor. The medium has a computer program stored on it that when executed by the processor causes the computer system to implement a method allowing a host processor and a modem to communicate both data and commands by multiplexing the information.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is system illustration of an exemplary PDA computer system connected to other computer systems and a modem via a cradle device.

Figure 2A is a top side perspective view of an exemplary PDA computer system.

Figure 2B is a bottom side perspective view of the exemplary PDA computer system of Figure 2A.

Figure 3 is an exploded view of the components of the exemplary PDA computer system of Figure 2A.

Figure 4 is a perspective view of the cradle device for connecting the exemplary PDA computer system to other systems via a communication interface.

Figure 5 is a logical block diagram of the exemplary PDA computer system, in accordance with an embodiment of the present invention.

Figure 6 is a front view of a exemplary PDA computer system illustrating the display screen, digitizer regions and an exemplary signal strength graph, in accordance with an embodiment of the present invention. Figure 7 illustrates an exemplary multiplexer with input data and commands and an output signal, according to an embodiment of the present invention.

Figure 8 is a block diagram of a PDA connected to a modem, illustrating logical units of the devices, according to an embodiment of the present invention.

Figure 9A, Figure 9B, Figure 9C, Figure 9D, Figure 9E, and Figure 9F illustrate exemplary fields within the exemplary frame structure, according to an embodiment of the present invention.

Figure 10A, Figure 10B, Figure 10C, Figure 10D, and Figure 10E illustrate exemplary frames which may be used in a procedure of a serial multiplexing protocol, according to an embodiment of the present invention.

Figure 1 1 illustrates the steps of a process of transferring commands and data without leaving a data mode, according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be obvious to one skilled in the art that the present invention may be practiced without these specific details. In other instances well known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the present invention.

NOTATION AND NOMENCLATURE

Some portions of the detailed descriptions which follow are presented in terms of procedures, steps, logic blocks, processing, and other symbolic representations of operations on data bits that can be performed on computer memory. These descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. A procedure, computer executed step, logic block, process, etc., is here, and generally, conceived to be a self-consistent sequence of steps or instructions leading to a desired result. The steps are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated in a computer system. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like. -1 fl¬

it should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussions, it is appreciated that throughout the present invention, discussions utilizing terms such as "processing" or "computing" or "translating" or "calculating" or "determining" or "scrolling" or "displaying" or "recognizing" or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices.

EXEMPLARY PERSONAL DIGITAL ASSISTANT PLATFORM

Figure 1 illustrates a system 50 that can be used in conjunction with various embodiments of the present invention. It is appreciated that the present invention can operate with a variety of host computers and that system 50 is merely exemplary. System 50 comprises a host computer system 56 which can be a desktop unit as shown or a laptop system 58. Optionally, one or more host computer systems can be used within system 50. Host computer systems 58 and 56 are shown connected to a communication bus 54, which in one embodiment can be a serial communication bus, but could be of any of a number of well known designs, e.g., a parallel bus, Ethernet Local Area NetWork (LAN), etc. Optionally, bus 54 can provide communication with the Internet 52 using a number of well known protocols. The bus 54 also provides a link between a modem 53a and any of the computer systems (100, 56, 58). In one embodiment, a modem 53b is integral to the PDA 100.

Importantly, bus 54 is also coupled to a cradle 60 for receiving and initiating communication with a personal digital assistant (PDA) 100, which may serve as the host computer system. The PDA 100 may be a palm top ("palm-sized") portable computer system, an intelligent cellular telephone, or the like. Cradle 60 provides an electrical and mechanical communication interface between bus 54 (and anything coupled to bus 54) and the computer system 100 for two way communications. Computer system 100 also contains a wireless infrared communication mechanism 64 for sending and receiving information from other devices. Figure 1 also contains a portable electronic device 55 which may be a cell phone, pager, or portable web-browser, etc. In one embodiment, the portable electronic device 55 serves as the computer system that communicates with a modem 53a.

Figure 2A is a perspective illustration of the top face 100a of one embodiment of the exemplary PDA computer system 100. The top face 1 10a contains a display screen 105 surrounded by a bezel or cover. A removable stylus 80 is also shown. The display screen 105 is a touch screen able to register contact between the screen and the tip of the stylus 80. The stylus 80 can be of any material to make contact with the screen 105. The top face 100a also contains one or more dedicated and/or programmable buttons 75 for selecting information and causing the computer system to implement functions. The on/off button 95 is also shown.

Figure 2A also illustrates a handwriting recognition pad or "digitizer" containing two regions 106a and 106b. Region 106a is for the drawing of alphabetic characters therein (and not for numeric characters) for automatic recognition and region 106b is for the drawing of numeric characters therein (and not for alphabetic characters) for automatic recognition. The stylus 80 is used for stroking a character within one of the regions 106a and 106b. The stroke information is then fed to an internal processor for automatic character recognition. Once characters are recognized, they are typically displayed on the screen 105 for verification and/or modification.

Figure 2B illustrates the bottom side 100b of one embodiment of the exemplary PDA computer system 100 that can be used in accordance with various embodiments of the present invention. An optional extendible antenna 85 is shown and also a battery storage compartment door 90 is shown. A communication interface 108 is also shown. In one embodiment of the present invention, the serial communication interface 108 is a serial communication port, but could also alternatively be of any of a number of well known communication standards and protocols, e.g., parallel, SCSI, Firewire (IEEE 1394), Ethernet, etc.

Figure 3 is an exploded view of the exemplary PDA computer system 100 in accordance with one implementation. System 100 contains a front cover 210 having an outline of region 106 and holes 75a for receiving buttons 75b. A flat panel display 105 (both liquid crystal display and touch screen) fits into front cover 210. Any of a number of display technologies can be used, e.g., LCD, FED, plasma, etc., for the flat panel display 105. A battery 215 provides electrical power. A contrast adjustment (potentiometer) 220 is also shown. On/off button 95 is shown along with an infrared emitter and detector device 64. A flex circuit 230 is shown along with a PC board 225 containing electronics and logic (e.g., memory, communication bus, processor, etc.) for implementing computer system functionality. The digitizer pad is also included in PC board 225. A mid-frame 235 is shown along with stylus 80. Position adjustable antenna 85 is shown.

A radio receiver/transmitter device 240 is also shown between the mid- frame and the rear cover 245 of Figure 3. The receiver/transmitter device 240 is coupled to the antenna 85 and also coupled to communicate with the PC board 225. In one implementation, the Mobitex wireless communication system is used to provide two way communication between system 100 and other networked computers and/or the Internet 52 via a proxy server.

Figure 4 is a perspective illustration of one embodiment of the cradle 60 for receiving the exemplary PDA computer system 100. Cradle 60 contains a mechanical and electrical interface 260 for interfacing with serial connection 108 (Figure 2B) of computer system 100 when system 100 is slid into the cradle 60 in an upright position. Once inserted, button 270 can be pressed to initiate two way communication between system 100 and other computer systems or to a modem 53a coupled to serial communication 265. Figure 5 illustrates circuitry of computer system 100, some of which can be implemented on PC board 225. Portions of the circuitry may also be used for computer system 56, 58 and modem 53. In particular, the processor 101 , ROM 103, RAM 102, and bus 99 may form a platform for those systems. Computer system 100 includes an address/data bus 99 for communicating information, a central processor 101 coupled with the bus for processing information and instructions, a volatile memory 102 (e.g., random access memory RAM) coupled with the bus 99 for storing information and instructions for the central processor 101 and a non-volatile memory 103 (e.g., read only memory ROM) coupled with the bus 99 for storing static information and instructions for the processor 101. Computer system 100 also includes an optional data storage device 104 (e.g., memory stick) coupled with the bus 99 for storing information and instructions. Device 104 can be removable. As described above, system 100 also contains a display device 105 coupled to the bus 99 for displaying information to the computer user. PC board 225 can contain the processor 101 , the bus 99, the ROM 103 and the RAM 102.

Also included in computer system 100 of Figure 5 is an optional alphanumeric input device 106 which in one implementation is a handwriting recognition pad ("digitizer") having regions 106a and 106b (Figure 2A), for instance. Device 106 can communicate information and command selections to the central processor 101. System 100 also includes an optional cursor control or directing device 107 coupled to the bus 99 for communicating user input information and command selections to the central processor 101. In one implementation, device 107 is a touch screen device incorporated with screen 105. Device 107 is capable of registering a position on the screen 105 where the stylus makes contact. The display device 105 utilized with the computer system 100 may be a liquid crystal device, cathode ray tube (CRT), field emission device (FED, also called flat panel CRT) or other display device suitable for creating graphic images and alphanumeric characters recognizable to the user. In the preferred embodiment, display 105 is a flat panel display.

Signal communication device 108, also coupled to bus 99, can be a serial port for communicating with the cradle 60 or directly to a modem 53. Device 108 can also include an infrared communication port.

Figure 6 is a front view of the exemplary PDA computer system 100 with a bar graph 305 showing signal strength of a radio frequency modem link, while data is also being received and displayed. Also shown are two regions of digitizer 106a and 106b. Region 106a is for receiving user stroke data for alphabet characters, and typically not numeric characters, and region 106b is for receiving user stroke data for numeric data, and typically not for alphabetic characters. Physical buttons 75 are also shown. Although different regions are shown for alphabetic and numeric characters, the present invention is also operable within a single region that recognizes both alphabetic and numeric characters. METHOD AND SYSTEM FOR SERIAL DATA MULTIPLEXER FOR CONTINUOUS COMMUNICATION WITH A MODEM WHILE IN DATA MODE The present invention provides for a method and a system that allow a host system and a modem to exchange commands (e.g., AT commands, etc.) and data without leaving a data mode. Referring to Figure 7, embodiments achieve this by encapsulating data 71 0 and commands 712 into data frames 702a and command frames 702b, respectively. The frames 702 are multiplexed into a signal 704. Both the host 100 and modem 53 may perform this process. In this fashion, embodiments of the present invention may efficiently exchange commands without leaving a data mode. Put another way, data and commands may be exchanged while in a single mode. Thus, embodiments of the present invention do not have substantial gaps between data exchange and command exchange. Furthermore, the communication link is not idle while one device waits for the other to reply to a command.

Figure 8 illustrates components of a PDA 100 and a modem 53, which are connected by a serial communication link 54. The PDA 100 and the modem 53 each have a command module 802, comprising a framer 812 that encapsulates commands 712 into command frames 702b. They each also have a data module 804, comprising a framer 812 that breaks longer input data elements 710 into data frames 702 (e.g., encapsulates data 710 into data frames 702a). The frames 702 are sent on to the multiplexers 706. In one embodiment, the modules (802, 804) also have software flow-control modules 816, which help control the sending and receiving of frames 702, based in part on available buffer 814 space. Conceptually, an embodiment may be said to comprise a command channel 820 and a data channel 822, which are multiplexed.

Still referring to Figure 8, in another embodiment, the data modules 806 are also operable to encapsulate a small group of commands 712, along with the data 710. For example, simple AT commands 712 such as reset modem 53, dial telephone, and hang-up telephone are sent over the data channel. Thus, in this embodiment the two channels supported by the multiplexing protocol are; a first channel (e.g., data channel 822) for simple AT commands 712 and data 710, and a second channel (e.g., command channel 820) exclusively for AT commands 712. In one embodiment, the data 710 is transferred in a fashion substantially compliant with point-to-point protocol (PPP). However, the present invention is not limited to using this protocol for data 710 transfer.

In the preferred embodiment, the data 710 which is transferred over the serial communication link 54 is encapsulated into frames 702. The frames 702 comprise several fields. Exemplary fields for the frame 702 are illustrated in Figure 9A though Figure 9F. The proper value may be set by the framer 812 to specify whether the frame 702 contains data 710 or command information. Referring to Figure 9A, a channel identification field is illustrated. For example, the MDM (modem) channel may be selected for transferring modem data 710. The command channel 820 (CMD) may be selected when transferring commands 712 (e.g., AT commands 712). In another embodiment, the modem (MDM) channel may be used to transfer selected commands 712, in addition to the data 710 For example, AT commands 712 for resetting the modem 53, dialing a telephone number, and hanging up the telephone line may be interspersed with the data 710 on the MDM (data 710) channel Allowing selected AT commands 712 to be transferred on the data channel 822 improves efficiency and simplifies the design

Figure 9B, illustrates a flag field, which is used for connection and disconnection requests and answers In the preferred embodiment, the host processor, for example, a PDA 100, is always in charge of initiating connection and disconnection requests However, the present invention is well-suited to allowing either device to initiate a connection or a disconnection

Referring now to Figure 9C, a receιve_max field is illustrated This parameter is used to indicate the maximum amount of data 710 which the device could receive, and hence, the maximum amount the other device could send This parameter is specified at connection time, and is re-freshed with each data 710 transfer The value is based on how much space is available in the device's buffer 814

Figure 9D illustrates a length field, which indicates the total length of the frame 702, including the header, but without the end mark Figure 9E illustrates an exemplary data field, which holds the data 710 passed over the communication link 54. The size of this field is variable. The maximum amount of data 710 allowed to be transferred may be based upon factors such as the size of AT commands 712 and replies, as well as the size of PPP frames, or the like. Figure 9F illustrates an exemplary marker field, which marks the end of a frame 702.

Figure 10A and Figure 10B illustrate exemplary frames 702, which are transferred between the host computer 100 and the modem 53 to open a connection (channel). In the preferred embodiment, the host processor 100 sends the connection request frame 702 shown in Figure 10A and the modem 53 replies with the frame 702 in Figure 10B. However, other embodiments allow either device to send either frame 702. In Figure 10A and Figure 10B, the value in the CHID (channel identification) field is '1 ', which specifies this channel is to be used for modem data 710, as opposed to commands 712. A value of '2', in this example, would indicate that this channel is for commands 712. The receive_max value is exemplary.

Figure 10C illustrates an exemplary frame 702 used to exchange information, for example, data 710 or a command 712. In one embodiment, each byte in the data stream is indexed by its position from the beginning of the stream (the connection). The receiving device indicates how much data 710 it is able to handle, by specifying a value in the receive_max field when the connection (channel) is opened. The sending device uses this value, along with the index to the data stream, to calculate how much data 710 and which data 710 to send to the receiver. The receiving device will indicate a new receive„max value when its free buffer 814 space changes.

Figure 10D and Figure 10E illustrate exemplary frames 702 for shutting down the connection (e.g., data channel 822 or command channel 820). In the preferred embodiment, the disconnect request is always issued by the host processor 100. In other embodiments, either the host 100 or modem 53 may issue the disconnect request.

Figure 1 1 illustrates the steps of a process 1100 of multiplexing commands 712 and data 710 for transfer between a host processor 100 and a modem 53. For clarity, this process describes a host 100 sending data 710 and commands 712 to a modem 53. More generally, the process allows two-way exchanges. In step 1 105, a data connection (channel) is established between the host processor 100 and the modem 53. In the preferred embodiment, this connection is established over a serial communication link 54, although the present invention is not limited to serial communication links.

In step 1 1 10, a command connection (channel) is established between the host processor 100 and the modem 53. In the preferred embodiment, the command channel 820 is used exclusively for commands 71 , while the data channel 822 is used for data 710 and commands 712 from a limited command set (for example, reset modem, dial telephone, and hang-up telephone commands 712). However, the command channel 820 is needed in order to transfer a command 712 from a substantially complete command set. For example, when status information such as the signal strength of a radio frequency modem is desired a suitable command is sent from the host 100 to the modem 53 This command may be from a set which comprises a substantial portion of the Hayes Standard AT Command Set In another example, When electronic-mail is received, the modem 53 may send to the host 100 a command 712 on the command channel 820 which indicates a message has been received

In step 1115, commands 712 and data 710 are encapsulated into separate frames 702 Additionally, a value is set in the frames 702 to indicate whether the frame 702 contains a command 712 or data 710

In step 1 120, the multiplexer combines data frames 702 and command frames 702 into a single stream It may be stated that the stream comprises multiplexed a data channel 822 and a command channel 820

In step 1 125, the multiplexed signal (stream) is transferred to the modem 53 The present invention is well-suited to transferring such a signal from the modem 53 to the host processor 100

In step 1 130, the modem 53 de-multiplexes the signal, using the channel identification value in the frames 702 The frames 702 are then sent to the appropriate module In step 1 135, the command frames 702 and data frames 702 are processed by their respective modules (802, 804) The preferred embodiment of the present invention, a method and system for a host system and a modem to exchange commands and data during data mode, using a multiplexed signal, is thus described. While the present invention has been described in particular embodiments, it should be appreciated that the present invention should not be construed as limited by such embodiments, but rather construed according to the below claims.

Claims

CLAlM VVc Claim:

1. A method for communicating between a computer system and a modem, comprising the steps of: a) establishing a connection between said computer system and said modem via a communication link; b) multiplexing data and a command to create a signal; and c) transferring said signal over said communication link.

2. The method of Claim 1, further comprising the step of: d) said modem receiving and responding to said command.

3. The method of Claim 1, wherein between steps a) and b) are the steps of: encapsulating data in a data frame; setting a value in said data frame to indicate that said data frame comprises said data; encapsulating a command in a command frame; setting a value in said command frame to indicate that said command frame comprises said command, such that in said multiplexing step of step b) multiplexing is of said data frame and said command frame to create said signal.

4. The method of Claim 1 or 2, wherein said step a) comprises the steps of: al) opening a data channel between said computer system and said modem; and a2) opening a command channel between said computer system and said modem.

5. The method of Claim 4, wherein said step b) comprises the step of: bl) multiplexing data on said data channel with a command on said command channel to create said signal.

6. The method of Claim 5, wherein said step b l) further comprises multiplexing commands on said command channel with data and commands from a limited command set on said data channel.

7. The method of Claim 6, wherein said limited command set comprises a reset modem command, a dial telephone command, and a hang-up telephone command.

8. The method of Claim 1 or 2, wherein said step b) comprises the steps of: bl) encapsulating said data in a data frame; b2) setting a value in said data frame to indicate that said data frame comprises said data; b3) encapsulating said command in a command frame; and b4) setting a value in said command frame to indicate that said command frame comprises said command.

9. The method of Claim 1 or 2, wherein said command indicates a request for signal strength information.

10. The method of Claim 1 or 2, wherein said command indicates that a message has been received.

11. The method of Claim 1 or 2, wherein said communication link is a serial communication link.

12. The method of Claim 1 or 2, wherein said computer system is a portable computer system.

13. The method of Claim 3, wherein said method is implemented in a computer system having a processor coupled to a bus, a computer readable medium coupled to said bus and having stored therein a computer program that when executed by said processor causes said computer system to implement said method for communicating between said computer system and said modem.

14. A communication system comprising: a host computer system; a modern; and a communication link connecting said host computer system and said modern, said host computer system and said modem operable to communicate over said communication link via a signal comprising multiplexed data and commands.

15. The communication system of Claim 14, wherein said host computer system and said modem are further operable to communicate commands and data while in a single mode.

16. The communication of Claim 14, wherein said commands are substantially compliant with the Hayes Standard AT Command Set.

17. The communication system of Claim 14, wherein said host computer system further comprises a command module operable to format a command into a command frame and to further indicate in said command frame that said command frame comprises a command, a data module operable to format data into a data frame and to further indicate in said data frame that said data frame comprises data, and a multiplexer operable to multiplex said command frames and said data frames.

18. The communication system of Claim 14, wherein said computer system is a personal digital assistant (PDA).

19. The communication system of Claim 14, wherein said computer system is a portable electronic device.

20. The method of Claim 3 or 13, wherein said step a) of said method comprises the steps of: al) opening a data channel between said computer system and said mode ; and a2) opening a command channel between said computer system and said modem.

21. The method of Claim 1 , 3 or 13, wherein said commands are substanlially compliant with the Hayes Standard AT Command Set.

22. The method of Claim 1, 3 or 13, wherein said computer system is a personal digital assistant (PDA).

23. The method of Claim 22, wherein said commands comprise a substantially complete set of the Hayes Standard AT Command Set.