Dynamic magnetic information storage or retrieval – Recorder control of an external device
Patent
1985-05-06
1987-12-15
McElheny, Jr., Donald
Dynamic magnetic information storage or retrieval
Recorder control of an external device
360 331, 358149, 370101, H04N 576, G11B 3100, H04J 306
Patent
active
047137029
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to data communication apparatus and more particularly to a data communication apparatus in which a bidirectional data communication between two apparatus can be made by a single signal line.
BACKGROUND ART
When a video signal picked up by, for example, a video camera is recorded by a video tape recorder (VTR), in order to operate these two apparatus in synchronism with each other, if the VTR, for example, is used as a master apparatus and the video camera as a slave apparatus, data signals containing a control signal, a mode signal, an answer signal and the like must be interchanged therebetween. In such case, in the prior art, as shown in FIG. 1, two signal lines 3 and 4 are generally interconnected between a master apparatus 1 and a slave apparatus 2. Then, in order that through the first signal line 3, a clock signal S1 (FIG. 2A) is transmitted from the master apparatus 1 to the slave apparatus 2 and that in synchronism with this clock signal S1, a data signal S2 (FIG. 2B) is transmitted from the master apparatus 1 to the slave apparatus 2, a data signal DT12, of time points from t.sub.1 to t.sub.2 is transmitted from the master 1 to the slave 2 or, in the reverse direction, a data signal DT21 of time points from t.sub.3 to t.sub. 4 is transmitted from the slave apparatus 2 to the master apparatus 1. In the case of FIG. 1, the level of the signal line 3 for the clock signal S1 is always maintained at logic level "1" so that during the interval t.sub.1 to t.sub.2 or the interval t.sub.3 to t.sub.4 in which each bit of the data signal DT12 or DT21 of, for example, 4 bits is transmitted, the level of this signal line falls down to logic "0" with a duty ratio of 1/2.
As described above, in the prior art, in order that the data signal S2 may be positively interchanged between the two apparatus without being dropped, it is important that while the two apparatus are being operated in synchronism with each other by the common clock signal S1, the data is interchanged bit by bit therebetween so as to prevent the transmission and reception of the data signal S2 from being overlapped in time.
However, according to the circuit arrangement of FIG. 1, the two signal lines 3 and 4 must be provided and hence this puts a restriction on simplifying the circuit arrangement of the control system as the total system including two apparatus.
DISCLOSURE OF INVENTION
In this invention, when a bidirectional communication of data between a master apparatus and a slave apparatus is carried out through a single transmission line, a transmission period of one apparatus and that of the other apparatus are formed as one block and this one block is repeated. Within one block, the transmission period of one apparatus and that of the other apparatus can be discriminated from each other and one block and another one block can also be discriminated from each other. Accordingly, in this data communication apparatus, the transmission and reception of data are respectively carried out in timing by a start signal from the master apparatus side and at least a start signal used to transmit the data from the slave apparatus to the master apparatus is always transmitted from the side of the master apparatus to the side of the slave apparatus at a predetermined cycle.
According to the present invention as mentioned above, since the transmission from the master apparatus and the transmission from the slave apparatus are carried out under the condition that both transmissions are formed as one block, they are respectively carried out during different periods having the predetermined sequential orders within one block and by the start signal from the master apparatus, both of the transmission and the reception are started, and both transmission periods are never overlapped with each other. Further, upon transmitting data from the master apparatus to the slave apparatus, on the basis of the transmitted start signal, data can be latched in the slave apparatus, while upon transmitting data from the slave app
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Ishihara Mitsugu
Machida Yukihiko
Eslinger Lewis H.
McElheny Jr. Donald
Sony Corporation
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