Method for controlling rotary memory device

Disclosed is a method for controlling a rotary memory device for recording information on a recording medium in the form of a track, in which method the respective areas, such as a count section, a key section and a data section, which constitute a record format in the form of a record, are stored in the respective sectors each having a fixed length.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a method for controlling a rotary memory device 
such as a magnetic disk memory for storing a record unit including an 
address section and a data section on a recording medium in the form of a 
track. 
2. Description of the Prior Art 
In a magnetic disk device such as used in a general purpose computor 
system, a fixed address for physically specifying a one-to-one 
correspondence, which is used in a main memory device, is not provided, 
but an address section (hereafter referred to as a count section) is 
provided for the identification of the information to be stored. Moreover, 
the length of a unit piece of information to be recorded (hereafter 
referred to simply as "the record") is variable and a specific flag called 
an address marker is attached to the head of a record so as to identify 
the beginning of the record. 
The widely used method of writing an address marker at the top of a record 
is to erase a portion of the recording medium by a direct current. This 
method is different from that for the writing of information and therefore 
a special circuit should be provided for the writing of the address 
markers. Further, the identification of address markers also needs a 
circuit different from that required for the reading of information. Thus, 
these additional requirements lead to an increase in the complexity of the 
overall apparatus. 
Moreover, since the identification of a record depends only upon the 
associated address marker, the hardware must be more complicated to assure 
the exact access to the beginning of information. 
SUMMARY OF THE INVENTION 
An object of this invention is to obviate the above-discussed drawbacks and 
to provide a method which enables a magnetic recording and reproducing 
system to eliminate resorting to a specific identifier such as an address 
marker the writing and identification of which require a specific circuit. 
According to this invention, a track is divided into plural regions having 
a fixed length (hereafter each region is referred to as a sector) and a 
signal or a sector pulse for indicating the beginning of each sector is 
generated when the beginning of the sector is reached. The signal may be 
detected by using a specific track provided only for the signal. When a 
record including at least an address section and a data section is stored, 
the address section is stored in a sector together with a piece of 
information (hereafter referred to as a flag) for distinguishing the 
stored address section from other information while the data section is 
stored in another sector posterior to the sector in which the address 
section is stored. The access to a record proceeds in such a manner as 
follows: First, the beginning of a sector is detected and then the 
associated flag is searched. When the flag is detected, the address 
section which follows the flag is read and the read-out address section is 
compared with the address information supplied externally. If there is a 
coincidence between the address section and the externally provided 
address information, the access to the data section stored in the 
posterior sector is made. 
In the case where the address information supplied externally includes a 
track address, a particular track address may be stored in at least one of 
the sectors of each track independently of the address section. According 
to that scheme, the accuracy of location of the head, after the head 
positioning operation, can be checked by comparing the track address read 
out of the associated sector with the track address included in an 
externally supplied address information. 
Moreover, each sector may store a piece of information representing the 
number attached to the sector in the area anterior to the area in which 
the address section of a record is to be stored (hereafter this piece of 
sector number information is referred to as a sector number). 
In that case, by reading out the sector number of a desired sector when an 
access is made to the desired sector, the desired sector can be searched 
on the basis of the read-out sector number.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Now, preferred embodiments of this invention will be described. In FIG. 1 
showing in block diagram a magnetic disk apparatus according to this 
invention, reference numeral 30 designates magnetic disks rotated by a 
mechanical power source not shown. A track 31 on a disk 30.sub.1 is called 
a data track and serves to store information therein. The data track 31 is 
divided into plural sectors each being the same and of fixed length. A 
track 32 on a disk 30.sub.2 is called a servo track and serves to store 
pieces of information, representing the beginning points of the respective 
sectors of the data track 31. Only one servo track 32 is required even in 
the case where more than two magnetic disks 30.sub.1 are used. It should 
here be noted that though only a single track is shown as provided on each 
magnetic disk, each disk may actually contain a multiplicity of concentric 
tracks. The other function of the circuit of FIG. 1 will be described 
later in detail. 
FIG. 2 illustrates the constitution of the information to be stored in a 
data track 31 as shown in FIG. 1. In FIG. 2, reference numeral 39 
indicates the beginning point of each sector and the region between such 
two points 39 forms a sector 40. Each point 39 is detected by a sector 
pulse produced from the servo track 32. Numeral 41 designates an 
information area which serves to store the physical address of the sector 
in which this information area is contained; 42 another information area 
which serves to store a record specified by the software; 43 a flag which 
is used to identify the record information area 42; 44 a buffer gap 
provided between adjacent sectors; and 45 a gap for separating the record 
information area 42 from the physical address area 41. Every area 41 has 
the same and fixed length and the same is true for every area 42, every 
flag 43, every gap 44 and every gap 45. Accordingly, in every sector 40, 
when read out, the physical address area 41, the flag 43 and the record 
information area 42 always appear at the same fixed locations with respect 
to the position at which the sector pulse 39 is detected. 
According to this invention, the conventional record having a variable 
length is recorded and reproduced after it has been transformed into a 
fixed-length format as shown in FIG. 2. 
FIG. 3A shows the constitution of the format of a record having a variable 
length. In the track A of FIG. 3, a reference numeral 46 indicates the 
beginning point of the data track and this point 46 is detected by an 
index marker; numeral 47 a home address section representing the address 
of the data track; 48 the count section of the first record (referred to 
as "record O") on the track; 49 the key section of the record O; 50 the 
data section of the record O; 51 the count section of the second record 
(referred to as "record 1"); 52 the key section of the record 1; 53 the 
data section of the record 1; and so on. 
According to this invention, the record information as shown in the track A 
of FIG. 3 is stored in the format shown in FIG. 2. Namely, as shown in 
FIG. 3, the home address 47 of the track A is necessarily written in the 
record information area 42 in a sector S#O. The home address 47 represents 
not only the track address but also the information about the state of the 
track in question, and is used to check whether or not the head is 
correctly positioned on the track and whether or not a proper track is 
chosen, and to start the reproducing operation correctly at the beginning 
of the track. 
The respective sections of the record O and the posterior records are 
stored sequentially in the successive sectors. Namely, the count section 
48 of the record O is stored in the record information area 42 of the 
sector S#1, the key section 49 of the record O is stored in the record 
information area 42 of the sector S#2, the data section 50 of the record O 
is stored in the record information area 42 of the sector S#3, and so on. 
If the data section 50 is so long, the information area of a single sector 
may not accommodate all of the information of the data section 50. In such 
a case, the excess portion of the data section 50 is stored in the record 
information area 42 of the next following sector. Thus, the data section 
50 may be stored in more than two successive sectors. The flags 43 in the 
respective sectors are represented in the hexadecimal coding, i.e. 
(26).sub.16 for the sectors storing the count sections and (OE).sub.16 for 
the other sectors. In the track B of FIG. 3, the gaps, which are inserted 
in the actual track, are omitted for brevity and therefore not shown. 
FIG. 4 shows the constitution of the information stored in the physical 
address area 41. In FIG. 4, reference numeral 61 designates the cylinder 
address of the data track in question, 62 the head address of the same 
data track, and 63 the sector number of the sector in question of the data 
track. Every cylinder address 61 and every head address 62 respectively 
remain the same in all the sectors of a data track while the sector 
numbers 63 are incremented for successive sectors. 
The apparatus shown in FIG. 1 performs a recording and reproducing 
operation in the format B as shown in FIG. 3, in such a manner as follows: 
The write/read operation will first be described. Apparatus in the upper 
stream, e.g. channel apparatus, supplies a writing information and an 
address information to a control apparatus 1 when the writing operation is 
performed while the channel apparatus supplies only an address information 
to the control apparatus 1 in the case of a reading operation. The writing 
information is stored in a data register 20 and the address information is 
stored in the group 10 of address registers 13, 14 and 15. 
The cylinder address, the head address and the record address of the 
address information are set in the cylinder address register 13, the head 
address register 14 and the record address register 15, respectively. A 
head positioning circuit 12 serves to position a magnetic head 25 properly 
on a desired data track. The head positioning circuit 12 causes the 
magnetic head to be shifted by receiving the contents of the cylinder 
address register 13 and the head address register 14. 
After this positioning operation, the information in the physical address 
area 41 just after the beginning point 39 of the sector is read out and 
the cylinder address 61 of the information is read in a bit-serial fashion 
so that the cylinder address 61 bit-serially read is set in a shift 
register 16. The content of the shift register 16 and the content of the 
cylinder address register 13 are sent to a control circuit 17 which 
compares one content with the other. 
If there is a coincidence between those contents, the head address 62 in 
the physical address area 41 is bit-serially read out and set in the shift 
register 16. 
Then, the contents of the shift register 16 and the head address register 
14 are received as inputs by the control circuit 17 which in turn compares 
the respective contents with each other. If there is a coincidence between 
the contents, it means that the magnetic head is properly positioned on a 
desired data track. 
Incidentally, the magnetic head passes by some sectors in the write/read 
operation and whether or not the positioning of the magnetic head is 
proper, may be checked through the same operation as described above by 
always reading out the contents of the physical address areas 41 of the 
respective sectors passed by. 
After it is determined that the magnetic head is positioned properly on the 
desired data track, the flag 43 is read out and set in the shift register 
16. The control circuit 17 checks whether the content of the shift 
register 16 is (26).sub.16 or not, and unless it equals (26).sub.16, the 
flag 43 of the next sector is not detected. Similar operations are 
repeated until the content of the shift register 16 is found equal to 
(26).sub.16. When the requirement is satisfied, the count section of the 
record information area 42 following the flag 43 is bit-serially read out 
and set in the shift register 16. Then, the content of the shift register 
16 and the cylinder address, the head address and the record address set 
in the address register group 10 are successively received by the control 
circuit 17 which in turn compares these addresses with those of the 
content of the shift register 16. If there is a coincidence between each 
of the sets of the corresponding addresses, the control circuit 17 writes 
in or reads out the key section in the record information area 42 of the 
next sector and further the data section stored in the record information 
area 42 of the second next sector. The information to be written in the 
data section is supplied from the data register 20 and the information 
read out of the data section is set in the data register 20. 
The sector number 63 in the physical address area 41 is used as follows: 
The count section specifies the byte lengths of the key section and the 
data section of the associated record and if the length of each of the gap 
44, the physical address area 41, the gap 45 and the flag 43 is fixed, it 
is possible by reading out the count section to calculate the distance to 
the count section of the next record in terms of the number of bytes. 
Accordingly, the control circuit 17 can obtain the sector number of a 
sector storing the next count section on the basis of the sector number of 
the previous sector storing the immediately previous count section. In 
this way, reliability in retrieving information can be much more improved 
by using both the flag 43 and the sector number 63 than by using only the 
flag 43 having a value of (26).sub.16. 
As described above, according to this invention, since the count section, 
the key section and the data section of a record stored in successive 
sectors can be respectively read out at fixed positions with respect to 
the beginning of the first one of the sectors storing the record, markers 
which are used in the conventional apparatus and need the provision of a 
special processing circuit having a complicated configuration, may be 
eliminated. 
Therefore, the apparatus as a whole can be simplified.