Electrical computers and digital data processing systems: input/ – Intrasystem connection – Bus interface architecture
Reexamination Certificate
1999-10-28
2003-03-04
Auve, Glenn A. (Department: 2181)
Electrical computers and digital data processing systems: input/
Intrasystem connection
Bus interface architecture
C710S062000
Reexamination Certificate
active
06529988
ABSTRACT:
TECHNICAL FIELD
The present invention is directed to relatively high speed transfer of data from a universal serial bus peripheral device to a personal computer. In particular, the present invention includes a method and apparatus for compression of data transferred over a universal serial bus.
BACKGROUND OF THE INVENTION
The universal serial bus (USB) is a computer bus architecture used for connection of information processing devices, such as peripheral computer devices to a personal computer (PC). For a number of reasons, use of a USB in peripheral device interconnection has become desirable. First, a wide range of information processing devices can be interconnected to other information processing devices, such as PCs, via the USB. For example, a PC's keyboard, mouse, printer, scanner, modem, audio devices and video devices, can all be connected via the USB. Also, the USB allows connection of these and other peripheral devices using only a single connector type. Additionally, device attachment is automatically detected by the USB and software automatically configures the device for immediate use, without user intervention.
FIG. 1
is a schematic diagram showing an earlier data transfer configuration in a USB/PC interconnection. A USB device
12
can be a keyboard, mouse, video device such as a CCD camera, or any other peripheral information processing device which can be connected wit a PC
14
via a USB
15
. A frame memory
16
is typically interconnected to USB device
12
to receive and temporarily store data therefrom. Frame memory
16
can be, for example, a first-in first-out memory (FIFO). A main control unit (MCU)
18
or central processing unit is connected to and controls the operation of the USB device
12
, the frame memory
16
and the USB
15
. It is also possible that a random access memory RAM
20
and program memory
22
be interconnected with the MCU. The RAM
20
and program memory
22
can be used for data compression as will be explained below. USB
15
includes a serial interface engine (SIE)
15
a
. SIE
15
a
transfers data initially generated by USB device
12
to PC
14
.
To capture data from USB device
12
and transfer the data to PC
14
, MCU
18
controls USB device
12
to capture the data. USB device
12
then transfers the data to frame memory
16
. MCU
18
then takes the data from frame memory
16
and transfers it SIE
15
a
for transfer to PC
14
. As shown in
FIG. 2
, SIE
15
a
includes a flip-flop
22
, a USB clock
24
and processing electronics
23
. The USB data is latched through input TX and output D+ of flip-flop
22
to processing electronics
23
for USB protocol processing and transfer to the PC
14
. USB clock
24
sets the rate for latching data through to processing electronics
23
.
USB clock can run at either a “slow” speed of about 1.5 MHz or a “fast” speed of about 12 MHz. The speed at which USB clock
24
is run depends upon the nature of USB device
12
. For example, a typical keyboard or mouse would probably be run at 1.5 MHz while a typical video camera would probably be run at 12 MHz. In the data transfer configuration shown in
FIG. 1
, on each USB clock cycle, data is read from TX input of flip-flop
22
and transferred to D+ output of flip-flop
22
. Processing electronics
23
reads data off the D+ output and, ultimately, the data is transferred to PC
14
.
FIG. 3
is a timing diagram showing the signals
32
,
34
, and
36
at D+, TX and USB CLK, respectively.
One of the tasks accomplished by processing electronics
23
is to place the USB data in “frames.” As shown in
FIG. 3
, under USB protocol, a frame
30
is a 1 millisecond (ms) interval in which data is transferred from the USB
15
to a PC
14
. However, also under USB protocol, each frame ordinarily can contain a maximum of 1023 bytes of data. When USB device
20
transmits 1023 bytes of data every frame, the remainder of the frame is ordinarily not used for data transfer. Thus, as shown by arrows
31
, running at 12 MHz, about 0.7 ms of the frame is used for data transfer while the remaining 0.3 ms is not.
It is often desirable that data from a peripheral device be transmitted relatively quickly to the PC to which the device is attached. And, in many cases, a relatively high transmission speed is desirable even at the expense of some resolution in the data. That is, it can be desirable to compress transferred data by discarding some data in order to gain speed in data acquisition. This can be the case, for example, when acquiring video or audio data from a peripheral device. In these types of signals, it is likely that a relatively lower transmission speed will have a greater effect on the ultimate quality of a sound or image than will relatively less, or reduced resolution, data.
Accordingly, it can be desirable to provide for compression of data from USB device
12
prior to routing data to PC
14
. In the earlier data transfer circuit shown in
FIG. 1
, data compression is achieved through the use of RAM
20
and software stored in program memory
22
. Data received from USB device
12
can be transferred to RAM
20
by MCU
18
. A compression program stored in program memory
22
can then operate to compress data stored in RAM
20
and MCU
18
can then transfer the compressed data to USB
15
. Generally, the compression program will act to remove some USB device data from that placed in RAM
20
. Thus, because there is less data to transfer to PC
14
, the transfer can take place more rapidly, facilitating a higher quality of sound or image to PC
14
.
However, there are a number of drawbacks in use of the data transfer system shown in FIG.
1
. First, even if data from USB device
12
is not being compressed, this data must be routed through MCU
18
prior to being fed into USB
15
. This can result in relatively slow transmission time. And, as noted above, relatively high transmission time can be advantageous when the USB device generates an audio or video signal. Additionally, using software to compress data before feeding the data into the SIE requires additional processing time.
As this discussion makes clear, there is need for improvement in transmission and compression of data from a peripheral computer device to a PC via a USB. Specifically, data compression should be able to be completed without additional processing time to facilitate relatively high transmission rates.
SUMMARY OF THE INVENTION
The present invention provides a hardware method an apparatus for transmission and compression of data from a USB device to a computer. The data transmission method transmits data directly from a data output of the USB device to a serial interface engine if the USB. In this way, data can be advantageously transferred relatively rapidly from the USB device to the computer. A data compression method and apparatus in accordance with the present invention achieves data compression without additional overhead processing time. Thus, data transfer speed acquired through data compression is not sacrificed due to added processing time.
The present invention includes an apparatus for transferring data from a first information processing device to a second information processing device via a universal serial bus (USB). The apparatus includes a serial interface engine (SIE) connected to the second information processing devices. The SIE is for transferring data from the first information processing device to the second information processing device. A data output, which outputs data at a given clock rate, is interconnected with the first information processing device. A latch is connected with the SIE and directly connected the data output. The latch is for reading data transferred from the data output of the first information processing device into the SIE at a given clock frequency. At least one clock generator drives the latch such that data is transferred directly from the data output of the first information processing device to the SIE.
By directly transferring data from the data output to the SIE, without first passing
Urade Masakazu
Yoshikawa Hiroto
Auve Glenn A.
Matsushita Electrical Industrial
Morrison & Foerster / LLP
LandOfFree
Method and apparatus for compression of universal serial bus... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for compression of universal serial bus..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for compression of universal serial bus... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3071735