JPH061604B2 - Gap control method in disk controller - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk controller that performs field-segmented format control, and more particularly to variable-length record processing that requires control of various gap lengths. It relates to a suitable variable length gap control method.

[Conventional technology]

Conventionally, when performing control to make the gap length variable, a storage area for setting the gap length itself is provided for each gap type, or no gap length storage area is provided as described in JP-A-54-109338. A method is known in which a gap length is set to a gap counter by a micro instruction every time a field is accessed and the gap is counted.

[Problems to be solved by the invention]

When various gap lengths are required, such as variable length record processing, in the above conventional technology, the former causes an increase in the amount of hardware, and the latter requires extra processing for setting the gap length for each field access. There is a problem that if the gap length is increased in order to cause data overrun or the like or to increase the processing time, the disk capacity is reduced.

An object of the present invention is to solve the above-mentioned problems and to provide a compact disk control device that suppresses an increase in the amount of hardware without deteriorating the performance.

[Means for solving problems]

First, FIG. 2 shows an example of a format in which fields are segmented. The fields 1, 2, ...
The data portion existing on the track is of a fixed length and a variable length. GAP1, 2, ... Are gaps for separating fields. In a field-segmented format, the gap and subsequent fields are grouped together, their length is a multiple of the segment length, and the variable length field is itself formatted to be a multiple of the segment length. . The gap length is a value unique to the disk device that is determined in consideration of the data transfer rate of the disk device and the command chain processing time, but there are several types corresponding to the fields as described above, and as a disk control device, It is necessary to control the gap lengths of multiple types existing on the track.

The present invention focuses on the fact that the gap length is expressed as segment length × N + M in the format in which the field is segmented, and the fractional part M is a value without the degree of freedom determined by the field type. Is used as a parameter of the gap length, and the segment number counting section of the gap counter first counts the segment length × N portion, and then counts the constant M portion determined by the field type to control the gap length. Is.

By means of the above means, the parameter for variably controlling the gap length need only have the quotient part of the true gap length divided by the segment length, the bit width of the comparator can be made small, and the gap length can be stored. It is possible to suppress an increase in the amount of hardware required to store it.

[Action]

From the beginning of the gap, the gap counter is updated with pulses at byte intervals that are synchronized with the rotation of the disc. At the stage when the next field is determined, one of the gap length storage areas where the value is stored in advance is selected and the gap counter is selected. Of the segment counter. When it is determined by this comparison that the counting of the segment length × N is finished, the constant M determined by the field is set in the gap counter until the next byte pulse arrives, and the update is started again. The detection of the end of the gap is performed when the value of the gap counter reaches a specific value.

〔Example〕

An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing one configuration of the gap counter control logic in the present invention. 1 is a gap length storage area for setting a quotient value obtained by dividing the true gap length value by the segment length. A data bus 2 serves as a path for setting a value in the gap length storage area 1. A bit clock signal line 34 is connected to the gap counter 3 to count the gap length while incrementing by a byte clock synchronized with the rotation of the disk. The gap counter 3 is 1
It is composed of a part 31 for counting the number of bytes in a segment and a part 32 for counting the number of segments. A load instruction signal line 35 for setting a value in the gap counter 3 and a reset instruction signal line 33 for initialization are connected. When the field type to be accessed next is instructed from the upper side, it corresponds to the field type stored in the gap length storage area 1, but is selected through the selector 4 by the field selection instruction line 5 and the number of segments of the gap counter 3 It is input to the comparator 6 so as to be compared with the counting section 32. When the comparison by the comparator 6 is coincident, the load instruction signal line 35 is output from the comparator 6 as a load instruction to the gap counter 3. Reference numeral 7 is a complement of the fractional part M obtained by segmenting the gap and is a constant which the control device itself has. When the up counter is used for the gap counter by setting the complement, the detection of the end of the gap by the decode output of the gap counter can be made common regardless of the field type. The constant is connected so that the value corresponding to the field type is selected through the selector 8 by the field selection signal 5 and loaded into the gap counter 3 as in the common gap length storage area. The output of the gap counter 3 is connected to the decoder 9, and the decoder 9 outputs the gap end detection signal 10. This gap end detection signal gives the timing of transition to control such as data transfer in the data field following the gap.

The above is the configuration of the gap counter control logic in the present embodiment, and the operation of this configuration will be described next.

In the gap length storage area 1, the number of segments for each gap type is set in advance by a micro instruction or the like. At the beginning of the gap, the gap counter 3 is initialized by the reset instruction signal line 33 and starts counting up by the byte clock 34 synchronized with the rotation of the disk. When the next field type is determined in the gap, the field selection instruction signal line 5 selects the gap length parameter corresponding to the gap by the selector 4, and the segment number counting unit 32 of the gap counter 3 and the comparator 6 Be compared. When the gap counter 3 counts up to the segment length × N, the inputs of the comparators match, so the comparator 6 outputs the load instruction signal 35 to the gap counter 3. At this time, it is loaded into the gap counter 3 through the constant 7 selector 8 corresponding to the field. This load operation is performed by the pulse of the next byte clock.
After loading, the byte clock signal line 34 continues updating. The output of the gap counter 3 is decoded, and when the value of the gap counter 3 becomes zero, the decoder 9 can output the gap end detection signal 10 to detect the end of the gap. If the segment length is a power of 2, a binary counter can be used as the gap counter 3, but even if it is not a power of 2, an appropriate P-adic counter can be used for the portion 31 for counting the number of bytes in the segment. Further, the gap end detection by the decoder 9 can be made common by switching the control of the gap counter 3 after loading to decrement without using the complement as the value of the fractional part M of the gap.

According to the present embodiment, since the size of the gap length storage area can be made smaller than that of the conventional method, it is possible to suppress an increase in the amount of hardware even for a variable length record format with many gap types.

In addition, by reducing the size of the gap length storage area and storing different gap length parameters in one area,
This has the effect of reducing the procedure for setting the gap length.

〔The invention's effect〕

As described above, in the variable length gap count control of the segmented field, there is an effect that the amount of hardware is suppressed and the procedure for setting the gap length is reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the gap counter control logic according to the present invention, and FIG. 2 is a detailed explanatory diagram thereof. 1 ... Gap length storage area, 2 ... Data bus, 3 ... Gap counter, 4 ... Selector, 5 ... Field instruction signal line, 6 ... Comparator, 7 ... Gap fractional value (complement), 8 ... Selector, 9 ... Decoder, 10 ... Gap end detection signal, 31
... Byte number in segment counting unit, 32 ... Segment number counting unit, 33 ... Reset instruction line, 34 ... Byte clock signal line,
35 ... Load instruction signal line.

Claims (1)

[Claims] 1. In a disk controller for controlling a format in which a field is composed of a series of fixed length areas called segments, a quotient obtained by dividing a true gap length by a segment length is used as a constant for a plurality of areas and a remainder part. As a variable length gap count control, which has a means for the control device and a gap counter for counting gaps in byte units, and the gap counter counts the gap in two stages by an integral multiple portion of the gap segment length and a remainder portion. Gap control method in a disk control device characterized by.