Electrical computers and digital data processing systems: input/ – Input/output data processing – Input/output data buffering
Reexamination Certificate
2003-02-24
2004-08-03
Perveen, Rehana (Department: 2182)
Electrical computers and digital data processing systems: input/
Input/output data processing
Input/output data buffering
C710S053000, C711S153000, C709S213000, C709S214000, C709S215000, C709S237000, C709S238000
Reexamination Certificate
active
06772242
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a communication device using three-step communication buffers and a data transmitting/receiving device, and more particularly, to a communication device using three-step communication buffers in which a serial communication device and a central processing unit can be always accessible to the three-step communication buffers.
2. Description of the Background Art
Generally, a large-scale integration circuit chip for communication and a circuit board for communication used in a serial communication terminal apparatus have a serial communication device (e.g. universal asynchronous receiver/transmitter, abbreviated UART) and a communication buffer for temporarily storing data therein. At this time, the communication buffer is provided to be accessible from two peripheral devices. The peripheral devices includes a serial communication device for transmitting and receiving data to/from an external device through a communication line, and a central processing unit for receiving data from the serial communication device or processing data to be transmitted through the serial communication device.
The transmitting/receiving device and the central processing unit use a communication buffer asynchronously, thereby accessing to the communication buffer at the same time. However, there is a disadvantage that incomplete data are accessed to cause an error to read and write unintended data.
The errors will be explained as follows in detail.
FIGS. 1A and 1B
are diagrams showing problems of the communication device using one communication buffer according to a related art, in which
FIG. 1A
shows a case that synchronization of data is broken and
FIG. 1B
shows a case that incomplete data reading is generated.
FIG. 1A
shows a case that the serial communication device
100
and the central processing unit
200
write data in one communication buffer
300
. At this time, the writing and the reading have a special direction. That is, the central processing unit
200
stores data from an upper layer of the communication buffer
300
to a lower layer, and the serial communication device
100
sequentially reads the data from the upper layer of the communication buffer
300
to the lower layer and thereby transmitting the data to an external device (not shown).
However, in this process, in case that the serial communication device
100
reads data to be transmitted in a state that the central processing unit
200
does not complete to write the data or the central processing unit
200
reads data previously stored in the communication buffer
30
before the serial communication device
100
stores newly received data in the communication buffer
300
by a processing speed difference resulted from asynchronization of the central processing unit
200
and the serial communication device
100
, data are not updated, that is, data do not have synchronism.
FIG. 1B
shows a case that the same storage region of the communication buffer
300
is simultaneously accessed by the serial communication device
100
and the central processing unit
200
. Herein, when the serial communication device
100
and the central processing unit
200
access to the same storage region of the communication buffer
300
at the same time, the data can be read incompletely.
Accordingly to this, in order to solve problems generated when one communication buffer is used, three-step communication buffers are used.
A communication device using three-step communication buffers according to the prior art and a method for transmitting/receiving data will be explained in detail with reference to attached drawings.
FIG. 2
is a construction view showing three-step communication buffers according to the prior art.
As shown in
FIG. 2
, the communication device comprises: a serial communication device
100
for transmitting/receiving data with an external device (not shown) in serial; a central processing unit
200
for processing data of an external device by accessing thereto or processing data of an inner device; three-step communication buffers BUF
1
, BUF
2
, and BUF
3
respectively designated by DOUT
1
_BUF_PTR, DOUT
2
_BUF_PTR, and DOUT
3
_BUF_PTR for temporarily storing the data; an interrupt generator
500
for generating interrupt to the central processing unit
200
; and a state buffer
400
for transmitting states of the respective communication buffers BUF
1
, BUF
2
, and BUF
3
to the central processing unit
200
.
A communication device using the three-step communication buffers according to the prior art and a method for transmitting/receiving data will be explained as follows.
Each of communication buffers BUF
1
, BUF
2
, and BUF
3
is set to have any one state of “reading”, “writing”, “waiting”, and “not using”. The setting is stored in the state buffer
400
. Then, the communication device designates the respective communication buffers BUF
1
, BUF
2
, and BUF
3
with the pointers DOUT
1
_BUF_PTR, DOUT
2
_BUF_PTR, and DOUT
3
_BUF_PTR by using state information stored in the state buffer
400
, thereby enabling to read and write.
According to this, a processing speed difference between the serial communication device
100
and the central processing unit
200
and an overlap of the processing location are not generated, thereby enabling to access to the respective communication buffers at all times.
Hereinafter, the communication device using the three-step communication buffers according to the related art and the method for transmitting/receiving data will be explained in detail.
1) A Method for Receiving Data
The serial communication device
100
selects one communication buffer BUF
1
to make into a data writing state. The communication buffer BUF
1
is selected as an example, and the other communication buffers BUF
2
and BUF
3
can be also selected. The communication buffer BUF
1
is designated and then received data are written in the communication buffer BUF
1
.
Subsequently, when the reception of the data is completed, the serial communication device
100
changes a state of the communication buffer BUF
1
into that of a communication buffer where recent data are stored. This state information is stored in the state buffer
400
.
Then, when the reception of the data is completed, the serial communication device
100
generates an interrupt to inform to the interrupt generator
500
that. The interrupt generator
500
applies the interrupt signal to the central processing unit
200
. Then, the central processing unit
200
checks the state buffer
400
, thereby checking in which communication buffer the recent data are stored.
If the central processing unit
200
checks the state buffer
400
, the communication buffer BUF
1
where the recent data are stored is converted into a reading state. Then, the central processing unit
200
accesses to the communication buffer BUF
1
converted into the reading state to read the stored data.
Like this, since at least one communication buffer among the three communication buffers BUF
1
, BUF
2
, and BUF
3
is not used in a process for receiving data or stores the recent data, the central processing unit
200
can access to the data at all times and an interference is not generated between the central processing unit
200
and the serial communication device
100
.
2) A Method for Transmitting Data
Contrary to said receiving method, the central processing unit
200
checks a readable communication buffer by the state buffer
400
, stores transmission data in the readable communication buffer BUF
3
, and converts state information of the communication buffer BUF
3
into a state that data to be transmitted are stored. Then, the serial communication device
100
receives a request to transmit data from the external device, designates a state of the communication buffer BUF
3
where the data are stored into a readable state, and reads the data from the buffer BUF
3
, thereby transmitting to the external device.
Like this, the communication device using the three communication bu
Greenblum & Bernstein P.L.C.
LG Industrial Systems Co. Ltd.
Perveen Rehana
LandOfFree
Communication device using three-step communication buffers does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Communication device using three-step communication buffers, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Communication device using three-step communication buffers will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3337763