Electrical computers and digital data processing systems: input/ – Input/output data processing – Transfer direction selection
Reexamination Certificate
1998-06-26
2001-09-04
Lee, Thomas (Department: 2182)
Electrical computers and digital data processing systems: input/
Input/output data processing
Transfer direction selection
C710S008000, C710S038000, C710S051000, C710S108000
Reexamination Certificate
active
06286060
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the field of computer electronics, and more particularly to input/output (I/O) functions of computing devices.
2. Background Art
The utility of a computer or computing device is often a function of the device's expansion capability. Most computing devices are equipped with one or more input/output (I/O) ports for connecting peripheral devices, such as modems, printers, card readers, etc. Different types of I/O ports may be used by different computing devices, such as, serial ports, infrared (IR) communication ports, and wireless (e.g., RF) communication ports. A computing device interconnected with one or more peripheral devices in this manner is referred to herein as a “host” computing device.
Peripheral devices serve to expand the available resources of a host computing device by, for example, adding communications, processing or storage capabilities. However, each host computing device is limited in its ability to support peripheral devices, and hence in its expandability, by the number and types of I/O ports provided. For example, a host computing device may be equipped with a single serial port, and be incapable of supporting any peripherals that use an IR port. Also, a host computing device may be equipped with one serial port and one IR port, but be incapable of supporting two peripheral devices that each require a serial port. Further, new types of communication ports may be developed in the future that may not interface with current communication port types. Thus, the hardware I/O configuration of the host computing device (i.e., the number and types of I/O ports) imposes limitations on the expandability of the host computing device.
Though it is a concern with most computing devices, the limitations of hardware I/O configurations can be more clearly illustrated with reference to small, portable computing devices such as personal digital assistants (PDAs), where the number of I/O ports is minimized to meet size constraints. To better understand the I/O limitations of computing devices such as PDAs, one example of a personal digital assistant is described below. In this example, the PDA is limited to a single serial port. The I/O limitations similarly exist for PDAs having a single port of a port type other than serial (e.g., IR, wireless, etc.).
The Personal Digital Assistant (PDA)
Unlike laptop computers, PDAs forego the use of a keyboard and a large display screen to maintain a compact shape capable, for example, of being carried in a pocket. In many PDAs, an electronic stylus and a small touch screen are employed for receiving user input, as well as for displaying the graphical output of the given application.
PDAs, such as the PalmPilot produced by 3Com Corporation, are designed to communicate with a personal computer to synchronize with databases located on the personal computer. Communication is achieved over an asynchronous serial link, for example, either directly with the personal computer or indirectly via a modem. Due to the desired dimensional limitations of the PDA, most PDAs have only one input/output (I/O) port, such as an RS-232 serial port, an IR port, or a wireless port. Thus, only one peripheral device matching the port type may be coupled to the PDA via the single I/O port, undesirably restricting the communication and expansion capabilities of the PDA.
FIG. 1
shows a PDA device (
100
) and a peripheral device (
103
) coupled via a serial connection. PDA device
100
is equipped with touch screen display
105
, mechanical buttons (
106
and
107
), an electronic stylus (not shown), and serial port
102
. A universal asynchronous receiver transmitter (UART)
101
is used to convert information from the PDA for transmission through serial port
102
, and to convert serial information received through serial port
102
. Mechanical buttons
106
are provided for user input, such as for the selection of predefined applications. Mechanical buttons
107
are provided for scrolling graphics on touch screen display
105
.
Touch screen display
105
is separated into application display area
108
and user input area
109
. Application display area
108
displays the graphical output of the current application being executed by PDA device
100
. User input area
109
contains software buttons
110
, alphabet script input area
111
, and numeric script input area
112
. Software buttons
110
are for performing system or application-based selection operations. Alphabet script input area
111
is used to enter alphabetical characters with the electronic stylus. Similarly, numeric script input area
112
is used to enter numeric characters with the electronic stylus. Character recognition software within the PDA converts user input in areas
111
and
112
into data characters.
Peripheral device
103
is equipped with serial connector
104
for coupling with serial port
102
of PDA device
100
. Peripheral device
103
may be, for example, a personal computer or modem as previously described, or another device designed to communicate through the serial port of the PDA.
FIG. 2
is a general block diagram of the data processing components within a PDA. For simplicity, all components are illustrated as being commonly joined to bus
205
. Other data paths between components may also be realized in PDA implementations. The components comprise display I/O
200
, processor
201
, button input
202
, memory
203
and I/O port
204
.
Display I/O
200
comprises the touch screen of the PDA and the video memory and driver circuitry required to display graphic output and receive touch screen input. Processor
201
comprises a microprocessor for executing sequences of instructions which embody the operating system and various applications of the PDA. Button input
202
comprises circuitry for responding to depressing of, for example, buttons
106
and
107
, and converting the depressing action of the buttons into input for processor
201
. Memory
203
comprises random access memory (RAM) for storing data and instructions for each application. Memory
203
may also include ROM (read-only memory) circuitry containing predefined system instructions. I/O port
204
comprises the driver circuitry and connection hardware for the single PDA I/O port, such as UART
101
and serial port
102
illustrated in FIG.
1
.
FIG. 3
is a general block diagram illustrating the interaction of a PDA software application with a serial I/O port. PDA device
100
comprises PDA application
300
executing on processor
201
. PDA application
300
is designed to communicate with a peripheral device, such as a personal computer. To achieve this communication, PDA application
300
sends data to, and receives data from, UART driver software
301
. UART driver
301
is responsible for controlling the conversion between the parallel data format of processor
201
and the serial data format of the serial port. UART driver
301
is assisted in the conversion process by the hardware of UART
101
.
UART
101
contains data buffers and timing hardware to implement data conversion, as well as to provide control over data transmission characteristics such as baud rate. Level conversion circuitry may also be present in UART
101
to provide RS-232 signaling compatibility. A serial link is formed between the PDA and a peripheral device by coupling the serial connector of the peripheral device to the serial port of the PDA, allowing UART
101
to transmit serial data to, and receive serial data from, the peripheral device.
Peripheral devices not configured to communicate through the serial port cannot interface with the PDA. For example, wireless RF devices and IR devices are not directly supported by the FDA. This is due, at least in part, to the compact design of the PDA, which has room for only one I/O port. The type of communication is therefore restricted to the port type implemented on the PDA.
Another drawback of conventional PDAs is that only one peripheral device of the given port type may be linked with the PDA. T
Bender Michael
DiGiorgio Rinaldo
Uhler Stephen
Lee Thomas
Peyton Tammara
Sun Microsystems Inc.
The Hecker Law Group
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