transferring a third I-Frame for end request of data DATA TRANSFER SYSTEM AND METHOD transfer to the second station from the first station
which completes the data transfer; BACKGROUND OF THE INVENTION then transferring a fourth I-Frame for end response of
The present invention relates to a data transfer 5 data transfer to the first station from the second station method by which digital information stored in a storage which responds to the end request of data transfer; medium is transferred to a remote place via a digital thus> terminating the data link corresponding to B network. channel.
According to an example of the conventional date 10 According to a second aspect of the present inventransfer method by which digital information is trans- tlon> m a date transfer system to be adapted to a digital ferred on a public line to a remote place, each of the network system wherein a data link can be arbitrarily transmit-side and receive-side provides a modulator- established or terminated between two stations so that a demodulator (i.e., MODEM). Herein, MODEM at the data transfer is performed between the two stations in transmit-side converts the digital information into an 15 accordance with a predetermined protocol, there is analog signal, which is then transmitted toward to the provided a date transfer system including: receive-side. Then, a MODEM at the receive-side de- * transmit-side station which compresses date read codes the analog signal into the digital information. from * *ton& medium to thereby transfer compressed
Meanwhile, in the above-mentioned data transfer data; and method wherein the digital information is transferred in 20 a receive-side station which expands the compressed the form of the analog signal, it takes a very long time date transferred thereto from the transmit-side station to transfer much information stored in a storage me- "nd then write it into a storage medium, dium such as a floppy disk. For this reason, there is wherein before transferring the compressed data, the provided another data transfer method in which the transmit-side station transmits a data transfer request to digital information is transferred in the form of a digital 25 the receive-side station, so that if the receive-side station signal. However, there is no data transfer method which is now ready to receive the compressed data, the transis optimum to the public network system, i.e., so-called mit-side station transfers the compressed data to the "ISDN" (Integrated Service Digital Network). receive-side station, while when completing a data
transfer, the transmit-side station transmits an end reSUMMARY OF THE INVENTION 30 quest of ^ transfer t0 the receivc.side station> ^ that
Accordingly, it is a primary object of the present if the receive-side station is now in a state to respond to invention to provide a data transfer method by which a data transfer completion, the data link formed bemuch information can be transferred to a remote place tween the transmit-side and receive-side stations is tervia ISDN with a short period of time. 35 minated.
It is another object of the present invention to pro- BRIEp DESCRIpTION QF THE DRAWINGS vide a data transfer method which can be implemented
with relatively low price but with high reliability. Further objects and advantages of the present inven
According to a first aspect of the present invention, in tion will be apparent from the following description,
a data transfer method wherein a data link correspond- 40 reference being had to the accompanying drawings
ing to B channel is established between first and second wherein a preferred embodiment of the present inven
stations which are connected together by a digital net- tion is clearly shown,
work corresponding to ISDN (i.e., Integrated Service In the drawings:
Digital Network) system so that a transmission control FIG. 1 is a sequence diagram showing a data transfer is made on a data transfer operation performed between 45 protocol for explaining a data transfer method accordthe first and second stations in accordance with a prede- ing to an embodiment of the present invention; termined LAP-B protocol, there is provided a data FIG. 2 is a block diagram showing a hardware contransfer method comprising steps of: figuration of a FD transfer unit;
transmitting a first I-Frame (i.e., Information Frame), FIGS. 3A, 3B are block diagrams each showing a
representing a data transfer request, from the first sta- 50 detailed configuration of en essential part of the FD
tion which functions as a transmit-side station to the transfer unit shown in FIG. 2;
second station which functions as a receive-side station; FIGS. 4A to 4F are drawings each showing a data
transmitting a second I-Frame, representing a re- configuration used in an embodiment of the present
sponse to the data transfer request, to the first station 5J invention;
from the second station which is now ready to perform FIG. 5 shows a detailed data configuration of data
a data transfer in response to the data transfer request; format used in an embodiment of the present invention;
sequentially reading out data from a first storage FIGS. 6 and 7 are data transfer sequences for explain
medium provided at the first station in response to the ing a data transfer procedure according to an embodi
second I-Frame, compressing read-out data, and then gg ment of the present invention,
transferring compressed data and an I-Frame of normal 1DTIAW „_ . „__., _
data, having information representing a data length and EM^BODIMFlJr
a transmission data number with respect to the com- fcMtf UDlMfc.N 1
pressed data, to the second station; Next, description will be given with respect to a
extracting the compressed data from the I-Frame of 65 preferred embodiment of the present invention by refer
normal data received in the second station, expanding ring to the drawings, wherein like reference characters
the compressed data, and thereby writing it into a sec- designate like or corresponding parts throughout the
ond storage medium provided at the second station; several views.
