Excavating
Patent
1988-07-14
1990-07-03
Atkinson, Charles E.
Excavating
371 32, G06F 1110
Patent
active
049397320
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention relates to a check of errors occurring in an information signal being transferred in a serial transfer form through a transmission line in a data processing system.
The data processing system is a system for integrating computers, memories and other data processing apparatus and comprises a first unit such as a channel unit, a second unit such as an input-output (IO) unit and a transmission line such as an interface line connecting the channel unit and the IO unit. In this disclosure, the channel unit, the IO unit and the interface line are defined the first unit, the second unit and the transmission line respectively, for simplicity hereinafter. The error check is performed at an interface circuit connected to the interface line and provided in the channel units and the IO units respectively.
As the processing speed or volume of the data processing system increases signal quantity transferred through the interface line increases. A signal transferred through the interface line, which will be called an "information signal " hereinafter, comprises a "data signal" and a "control signal". The data signal is a signal, for example, to be stored into or read out from a memory such as a main memory in the data processing system or a buffer memory in the IO unit. The "control signal" is a signal for controlling the data signal so as to be, for example, sent to some unit in the data processing system, stored into or read out from the memory.
2. Background Art
Formerly, coaxial cables were used as the interface line. However, when a coaxial cable is used, the information signal cannot be transferred at high speed because of a stray capacity distributed along the coaxial cable. Accordingly, many coaxial cables as much as one hundred had to be equipped for the interface line. Further, the size of each coaxial cable is not small. Accordingly, a large space was needed for the coaxial cables. To reduce the space, there is a parallel-series signal converting technique (P-S converting technique) for converting the information signals given in parallel into those in series. However, the P-S converting technique actually could not be applied to the coaxial cables because it still took too much time to transfer the information signal due to the stray capacity. The P-S converting technique has been brought into full play after an optical fiber technology has been established.
As is well known, the optical fiber is very small in size and has an excellent signal transfer speed. Applying the optical fibers to the interface line, the P-S converting technique became effective for the first time in transferring the information signal in a serial transfer form with successive frames. To arrange the information signal in the frames, a data buffer was used in the way that every time the information signal was transferred, bytes of the information signal were stored once into the data buffer and read out one by one, forming the frames. However, as long as the data buffer was used, the speed of the signal transfer was limited to low one, and there was a possibility that a trouble called "command overrun" would have occurred. These problems have been solved by introducing dummy codes into the frame instead of using the data buffer. The dummy codes are used so as to be always transferred between the channel unit and the IO unit through the interface line when there is no information signal to be transferred and replaced by the bytes of the information signal at any time the information signal is given to be transferred. However, there are still problems with the method and circuits for implementing the dummy codes technique, and the present invention is for solving the problems.
Before disclosing the present invention, the prior art frame construction, and the dummy codes and the information signal arranged in the frame will be explained, referring to FIGS. 2 and 3.
FIG. 2 shows an example of a frame construction 30 composed of a frame header 1, a plurality of signal transfer units 32,
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Endo Kazuhiko
Mikuni Tamotsu
Miyazawa Kazuyoshi
Nishimura Kousuke
Okamoto Koichi
Atkinson Charles E.
Fujitsu Limited
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