Electrical computers and digital processing systems: memory – Storage accessing and control – Shared memory area
Reexamination Certificate
1998-07-29
2001-04-24
Ellis, Kevin L. (Department: 2185)
Electrical computers and digital processing systems: memory
Storage accessing and control
Shared memory area
Reexamination Certificate
active
06223261
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a communication device, and more particularly, to a communication device comprising a utilization portion for performing arbitrary application processing, a control portion for performing processing in accordance with a previously determined protocol, and a memory which is shared between the utilization portion and the control portion, a communication method, and a medium on which a computer program for carrying out the method is recorded.
2. Description of the Background Art
In a communication device comprising a utilization portion for performing arbitrary application processing, a control portion for performing processing in accordance with a previously determined protocol, and a memory which is shared between the utilization portion and the control portion, the control portion transmits transmit data generated in the utilization portion in accordance with the previously determined communication protocol. In the communication device, when large amounts of transmit data are generated in the utilization portion for a short time period at a speed exceeding the communication speed of the control portion, the transmit data may be discarded without being transmitted. Therefore, the conventional communication device has a transmission buffer provided therein, and employs a method of temporarily storing transmit data in the transmission buffer to absorb the overflow of the transmit data.
Description is now made of the conventional communication device which is provided with the transmission buffer.
FIG. 24
is a block diagram showing an example of the structure of a transmission portion in the conventional communication device. In
FIG. 24
, the communication device comprises a control portion
1010
, a utilization portion
1020
, a RAM (Random Access Memory)
1030
, and an interface
1040
.
The control portion
1010
executes a previously determined communication protocol. Although the utilization portion
1020
performs application processing, no service for using is specified on the communication protocol. That is, a user can use an arbitrary application program in the utilization portion
1020
.
The RAM
1030
is used as a working memory of the control portion
1010
and the utilization portion
1020
. The RAM
1030
has, as ones related to transmit data, a transmission buffer
1031
, a transmit data management table
1032
, and an untransmitted data management table
1033
. The transmission buffer
1031
and the transmit data management table
1032
are under the management of the utilization portion
1020
. On the other hand, the untransmitted data management table
1033
is under the management of the control portion
1010
. The details of the transmission buffer
1031
, the transmit data management table
1032
, and the untransmitted data management table
1033
will be described later.
The control portion
1010
is connected to a communication line
1042
through the interface
1040
. The interface
1040
includes a modem or the like, and mediates communication between the communication device shown in FIG.
24
and another communication device (not shown).
FIG. 25
is a diagram showing the structure of the transmission buffer
1031
shown in FIG.
24
. Transmit data generated in the utilization portion
1020
is written into the transmission buffer
1031
. In
FIG. 25
, eight transmit data are written, as an example, into the transmission buffer
1031
.
FIG. 26
is a diagram showing the structure of the transmit data management table
1032
shown in FIG.
24
. The location of each of the transmit data written into the transmission buffer
1031
is contained in the transmit data management table
1032
as shown in
FIG. 25
(specifically, a head address in a write area of the each of the transmit data in the transmission buffer
1031
).
FIG. 27
is a diagram showing the each of the structure of the untransmitted data management table
1033
shown in FIG.
24
. The untransmitted data management table
1033
stores the location of each of the transmit data whose request for transmission has been accepted (a head address in a write area of the each of the transmit data in the transmission buffer
1031
) and the size thereof. Further, a header information write area and an ender information write area are provided in relation to the location and the size of each of the transmit data.
FIG. 28
is a flow chart showing a part of operations performed by the utilization portion
1020
shown in FIG.
24
.
FIGS. 29 and 30
are flow charts showing parts of operations performed by the control portion
1010
shown in FIG.
24
.
Referring now to
FIGS. 28
to
30
, description is made of a series of operations performed from the time when transmit data is generated until it is transmitted in the communication device shown in FIG.
24
.
FIG. 28
will be referred to. The utilization portion
1020
judges, when transmit data is generated (step S
2801
), whether the transmission of the transmit data is the first transmission or the second or later transmission (step S
2802
). In the case of the first transmission, the utilization portion
1020
judges whether or not the transmit data management table
1032
has a space (step S
2803
). In the first transmission, the transmit data management table
1032
is empty, so that the result of the judgment is “YES”, after which the program proceeds to the step S
2804
. At the step S
2804
, the utilization portion
1020
judges whether or not a write area in which transmit data is to be newly written can be ensured in the transmission buffer
1031
. In the first transmission, the transmission buffer
1031
is empty, so that the result of the judgment is “YES”, after which the program proceeds to the step S
2805
. At the step S
2805
, the utilization portion
1020
ensures a write area in which transmit data is to be newly written in the transmission buffer
1031
, to add the location (a head address) of the ensured write area to the transmit data management table
1032
. The utilization portion
1020
then writes transmit data generated at that time into the newly ensured write area in the transmission buffer
1031
(step S
2806
). The utilization portion
1020
then prepares a data transmission request (step S
2807
). The data transmission request includes the location of the transmit data newly written into the transmission buffer
1031
and the size thereof. The data transmission request is outputted to the control portion
1010
at the step S
2808
.
FIG. 29
will be referred to. The control portion
1010
adds, when it receives the data transmission request from the utilization portion
1020
(step S
2901
), the location and the size of the transmit data (both are included in the data transmission request) to the untransmitted data management table
1033
(step S
2902
). The control portion
1010
then writes header information of a packet to be later generated in a header information write area in the same column as a column to which the location and the size of the transmit data are added at the step S
2902
(step S
2903
). Further, the control portion
1010
then writes ender information of the packet to be later generated in an ender information write area in the same column (step S
2904
). The control portion
1010
then judges whether or not the communication device is currently in a transmittable state (step S
2905
). Such judgment is required because the communication device shown in
FIG. 24
makes half-duplex transmission, for example, so that it cannot transmit the transmit data while receiving transmit data from a communication device at the destination of communication (not shown). The control portion
1010
performs processing at the step S
2906
immediately when transmission is possible, while performing the processing after waiting, when transmission is impossible, until there occurs a state where transmission is possible. At the step S
2906
, the control portion
1010
generates a packet for the oldest transmit data out of the transmi
Ellis Kevin L.
Matsushita Electric - Industrial Co., Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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