JPS58171776A - Detection for address mark of magnetic disc device - Google Patents

Abstract

PURPOSE:To prevent the lowering of the use efficiency of a magnetic disc device, by detecting an address mark again without stopping the operation when a flaw on the surface of a recording medium is mistaken for the address mark. CONSTITUTION:When an address mark detecting instruction is inputted from a terminal AM, this instruction passes through a NOR circuit 1 to set a terminal S of a flip flop 2 to ''0'' and set an output terminal SAM to ''1''. A data read signal is inputted from a terminal DATA, and the output of an AND circuit 3 becomes a signal DATA, and an AM detecting circuit 4 starts detecting an address mark AM. When a skip defect SD is mistaken for the address mark AM, a terminal AFN of the AM detecting circuit 4 becomes ''0'', and a terminal AFN' becomes ''1''. Consequently, the flip flop 2 is reset, and the terminal SAM becomes ''0''. A counter 5 starts counting bytes with byte clocks; and when five bytes are counted, a flip flop 6 is set, and a terminal SBS is set to ''1''.

Description

Detailed Description of the Invention (a) Technical Field of the Invention The present invention relates to a method for treating defects on the surface of a medium recorded by a variable length magnetic recording system in a magnetic disk device. The present invention relates to an address mark detection method for a magnetic disk drive that detects an address number.

Conventional technology and problems A typical format for tracks formed on a magnetic disk medium using a variable length magnetic recording system is shown in Figure 1.
B is an index mark indicating the track-circumference reference point, HA is the home address, C is the count field, S
B is the start mark of the record and synchro byte, D is the data field, RO, R1, R2, R3 are the record, A
M is an address mark, and 8D is a skip defect, indicating the position where there is a scratch on the magnetic disk recording surface -F, and the scratch has been completely skipped using the medium surface defect processing method.
Since this is a variable length magnetic recording system, the length of the data field D after record R1 changes depending on the amount of data to be recorded. However, since one address mark AM is placed at a certain distance from each record starting from record R1, the magnetic disk controller A, which is a host device, can see the address no matter where on the track circumference the magnetic head is located. - A fault detection command is issued.

In conventional magnetic disk manufacturing, for example, if there is a magnetic head in front of a scratch indicated by SD (MIWJ skip defect) and an address mark detection command is received, the interval of skip defect 8D is determined by the size of the scratch I. If the interval is almost the same, skip defect SD meeting address mark AM and ll4Ii! ! In some cases, the address mark AM detection bond - within the time - synchro byte S which is the first mark of record R3 that should exist.
Since R is not detected, a report that the record does not exist is sent to the upper level device, which has the disadvantage that the usage efficiency of the magnetic disk device is reduced and the system operation is also affected.

(c) Purpose of the Invention The purpose of the present invention is to eliminate the above-mentioned drawbacks, and when a skip defect SD1 is mistakenly identified as an AM address, the V address is re-addressed before being reported to the host device. - Detecting the correct address mark AMt will increase the operating efficiency of the magnetic disk drive.

(dl Structure of the Invention The structure of the present invention includes a circuit for detecting an address mark, a circuit for detecting a synchronized byte, which is the first mark of a record, and a circuit for detecting data near the beginning of a record. If the sync byte is not detected after a certain period of time, it is assumed that the address mark is statically detected, and the front page dress mark detection is reset and the address mark detection operation is performed again to detect the correct address mark. If the synchro byte is detected incorrectly even though the synchro byte is detected, there is a risk of reading another record.Existence of a bit that is 1 or more @1'' while detecting the synchro byte of the record t - If detected, the address This is done so that the mark re-detection operation is not performed.

(.) Embodiment of the Invention FIG. 2 is a block diagram of a circuit showing an embodiment of the invention. FIG. 3 is a time chart explaining the operation of FIG. The symbol in Fig. 3 shows the waveform of the No. 2 terminal in Fig. 2. When the address mark detection command is input from AM, N0R (
b) S terminal of flip frog 2 via path 1'[@θ''
It is assumed that the output terminal is SAM 11'. A data extraction signal is input from the DATA terminal, and the output of the ANDl1g circuit 3 is D.
It becomes an ATA signal and the AM detection circuit 4 detects the address mark AM.
The discovery meeting begins. Favorite and defective SII address shown in Figure 3 track format! - If it is mistaken as AM, the AFN terminal of AM detection circuit 4 becomes @0# and AFN
g! 14 children becomes 11″. Therefore, flip frog 2
is reset and the SAM terminal becomes @01. Also, the counter 5 starts counting by the byte clock, and when it counts 5 bytes, it sets 7 rip, 70 lub, 6t, and connects the SBS terminal' (H
When the SBS terminal of the flip-flop 6 becomes 1", the output of the ANDβ circuit 7 becomes the DATA signal and detects Br. When the circuit 8 is activated, an attempt is made to detect the synchronized byte SBk, which is the first mark of the record, but the skip defect (SD't address mark that has been processed due to scratches on the recording medium) is 1.
Approved. Synchro byte S that appears after 5 bytes
B is not detected. Even if 22 bytes are detected, the sync date byte SB is not detected, so the output SBF of the 8B detection circuit 8 is
is the platform of “1”. The output of the counter 5 after counting 5 bytes also sets the 7 lip-flop 10, indicating that the DAR terminal 11'' is the data area.

The AND circuit 11 becomes 11" together with the data extraction signal of the DATA terminal, and the data presence/absence detection circuit 12t is activated. The data presence/absence detection circuit I2 has no record, so data cannot be detected. ■〒1 terminal is "1"It's Noma\.

The flip-flop 6 is reset by the signal after counting 22 bytes of the counter 5, and when 5BSi child 1; t-1- is reached, A
Since the DAR terminal of the flip-flop lO is still at “1”, the ND circuit x 3 sets the output to 11 and performs a NOR operation.
Circuit 1 [4! Set Flip 70 Tsug 2 again
M terminal t''''l'', and AM via NOR circuit 9Vr
Detection circuits 4 and 7 are reset to 10Vt.

As the SAM terminal of the flip-flop 20 becomes ``1'' again, the -CAM detection circuit 4 becomes active as described above and detects the address mark Mt-. Similar to the above, the SB detection circuit becomes active and detects the synchro byte 8Bk, which is the first mark of the record, and the 101 terminal becomes "0", and the D of the data presence/absence detection circuit, which is in the "-active" state, as described above.
The TP terminal is also a data when the record data is 1 or more and 11"! [When detected, it becomes "0". When the reading of the data in the count field C of the record is completed, the END signal is sent, so it passes through the NOT circuit 9\r. The AM detection circuit 4 and the 7-lip 70-tub 10 are reset, and at the same time, the SBB output circuit 8 and the data presence/absence detection circuit 12 are also reset.

If the regular address mark AMt is detected but the synchro pie) SR cannot be detected, the SB side output circuit 8SBFB child is @l” t\, but the DTP terminal of the data presence/absence detection circuit is 1 or more. If the data corresponding to l# is detected, it becomes "0m", so the output of the AND circuit 13 becomes a trench of 10".

Therefore, since the flip-flop 2 is not set again, the AM detection circuit 4 also does not operate and the address mark AM is not detected again. By reporting this state to the upper level device, all abnormal conditions can be reported.

(f) Effects of the Invention As explained above, the present invention improves the usage efficiency of magnetic disk drives because even if a scratch on the surface of a recording medium is misidentified as an address mark, the address mark is detected again without stopping the operation sound. The effect is great because it often lowers the temperature and therefore does not affect the operation of the system.

[Brief explanation of the drawing]

tx1 is a diagram showing a normal formatter for tracks formed on a magnetic disk medium, FIG. 2 is a circuit diagram showing an embodiment of the present invention, and FIG. 3 is a time diagram explaining the operation of FIG. 2. It is a chart. 1.9 is a NOR circuit, 3, 7. 1 and 13 are AND circuits, 2m s-1o is a flip-flop, 4 is an AM detection circuit, 5 is a counter, 8 is an SBB output circuit, and 12 is a data presence/absence detection circuit.

Claims (1)

[Claims] In a method for detecting an address mark recorded by a variable length magnetic recording method of a magnetic disk device, there is provided a method for detecting an address mark [means for detecting the address mark], and a method for detecting an address mark recorded at a predetermined distance from the address mark. A means for detecting a head mark of a record, and a means for detecting data of the record.If the head mark of the record and the data of the record are not detected after detecting the address mark, the rear address mark detection is reset and restarted. If the address mark detection operation is performed and the first mark of the record is not detected and data of the wrinkle record is detected, the address mark re-detection operation VrIl!
An address mark detection method for a magnetic disk device in which a 1-stop image is used as a t4I image.