JPH04221463A - Floppy disk controller - Google Patents

Abstract

PURPOSE:To prevent a hangup from being caused when a data is read out, in a double-density recording made, from a floppy disk on which the data has been recorded according to a single-density recording system by a method wherein a floppy disk controller is used. CONSTITUTION:When a sink field is detected by using a sink address mark detection circuit 4, a one-byte elapsed signal (k) at a byte counter 5 is counted by using a control circuit 6. When a data input detection signal (g) at a data shift register 3 does not become active even when the one-byte elapsed signal (k) at the byte counter 5 is counted by the number of bytes in the sink field by using the control circuit 6, the sink field is detected again by using the sink address mark detection circuit 4.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a floppy disk controller.

0002

2. Description of the Related Art Generally, when data recorded on a floppy disk is read by a floppy disk controller, a sync field is detected, an address mark is detected, and then the data field read operation is started. In addition, after detecting the sync field, if an address mark cannot be detected within 1 byte after the first data bit (the first bit at the beginning of the data) is input, the address mark will not be detected and the sync field will be re-entered. Discovery is performed.

0003

[Problems to be Solved by the Invention] However, in conventional floppy disk controllers, when reading data from a floppy disk recorded using the single-density recording method in double-density recording mode, the first data The problem was that no bits would be input and the floppy disk controller would hang up waiting for the first data bit to be input.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to solve the problem that even when reading data from a floppy disk on which data has been recorded using a single-density recording mode in a double-density recording mode,
To provide a floppy disk controller that does not cause hang-up.

[0005]

[Means for Solving the Problems] A floppy disk controller of the present invention includes a data separate circuit that receives read data and a window from a floppy disk drive and outputs a separate clock, separate data, and a shift clock; a clock shift register that receives a shift clock as an input and outputs a parallel clock signal; a data shift register that receives separate data and a shift clock as an input and outputs a parallel data signal and a data input detection signal having the same bits as the clock signal; A sync/address mark detection circuit receives a clock signal and a data signal as input, detects a sync field and an address mark, and outputs a sync/address mark detection signal, and receives a shift clock as input, counts the number of bytes of read data, and detects 1 byte. A byte counter that outputs a 1-byte elapsed signal each time a byte elapses, a sync/address mark detection signal, a data input detection signal, and a 1-byte elapsed signal are input, and the 1-byte elapsed signal is counted by the number of bytes in the sync field. When the sync field is detected by the sync address mark detection circuit, even if the control circuit counts the 1-byte elapsed signal of the byte counter for the number of bytes of the sync field, the data input of the data shift register is not detected. When the signal does not become active, the sync field is detected again by the sync address mark detection circuit.

[0006]

[Operation] According to the configuration of the present invention, when the sync field is detected by the sync address mark detection circuit, the byte counter counts the number of bytes of read data and inputs a 1-byte elapsed signal to the control circuit every time 1 byte elapses. Then, the control circuit counts the 1-byte elapsed signal. Then, even if the control circuit counts 1-byte elapsed signals for the number of bytes in the sync field, if the data input detection signal input from the data shift register to the control circuit does not become active, the sync address mark detection circuit , re-detect the sink field.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing the configuration of a floppy disk controller according to an embodiment of the present invention, and FIG. 2 is a flowchart for explaining the operation of the floppy disk controller. As shown in FIG. 1, the floppy disk controller includes a data separation circuit 1, a clock shift register 2, a data shift register 3, a sync/address mark detection circuit 4, a byte counter 5, and a control circuit 6.

The data separation circuit 1 inputs read data a and a window b from a floppy disk drive (not shown), and outputs a separate clock c, separate data d, and a shift clock e. The clock shift register 2 is connected to the data separation circuit 5
It inputs the separate clock c and shift clock e from , and outputs an 8-bit parallel clock signal (hereinafter referred to as "8-bit parallel clock signal f").

The data shift register 3 receives separate data d and shift clock e from the data separation circuit 5, and receives a data input detection signal g (indicating the input of the first data bit) and an 8-bit parallel data signal. (Hereinafter referred to as "8-bit parallel data signal h".)
Output. The sink address mark detection circuit 4 has 8
It inputs a bit parallel clock signal f and an 8-bit parallel data signal h, detects a sync field and an address mark, and outputs a pattern matching signal i which becomes a sync address mark detection signal.

The byte counter 5 inputs the shift clock e, and uses the shift clock e to count the number of bytes of the read data a input from the floppy disk to the data separation circuit 1. A byte progress signal is output to the control circuit 6. Further, a reset signal j from the control circuit 6 is input. The control circuit 6 receives a data input detection signal g and a pattern matching signal i.
and the 1-byte elapsed signal k are input, and the 1-byte elapsed signal k from the byte counter 5 is counted by the number of bytes of the sync field.

The operation of the floppy disk controller configured as described above will be explained below. When performing a read operation, read data a and window b are input to the data separation circuit 1 from a floppy disk drive (not shown). Thereby, the data separate circuit 1 inputs the separate clock c and the shift clock e to the clock shift register 2, and inputs the separate data h and the shift clock e to the data shift register 3.

The clock shift register 2 inputted with the separate clock c and the shift clock e outputs an 8-bit parallel clock signal f to the sync address mark detection circuit 4. Furthermore, the data shift register 3 to which the separate data h and shift clock e are input,
An 8-bit parallel data signal h is output to the sync address mark detection circuit 4.

In the sink address mark detection circuit 4,
The shift field is detected using the 8-bit parallel clock signal f from the clock shift register 2 and the 8-bit parallel data signal h from the data shift register 3 (see FIG. 2). Here, when a sink field is detected, by activating the pattern matching signal i, the control circuit 6 outputs a reset signal j to the byte counter 5 and resets the byte counter 5 (see Figure 2).
. The reset byte counter 5 counts the number of bytes of the read data a using the shift clock e from the data separation circuit 1, and counts the number of bytes of the read data a every time one byte elapses.
An active 1-byte elapsed signal k is output to the control circuit 6. The control circuit 6 counts the 1-byte elapsed signal k until the data input detection signal g of the data shift register 3 becomes active. If the data input detection signal g of the data shift register 3 does not become active even after counting the 1-byte elapsed signal k for the number of bytes in the sync field, the sync address mark detection circuit 4 again detects the sync field. (Figure 2)
, see ).

Furthermore, if the data input detection signal g of the data shift register 3 becomes active while the control circuit 6 is counting the 1-byte elapsed signal k, the sink address mark is detected after 1 byte has elapsed from that point. The address mark is detected by circuit 4 (Fig. 2■, Fig. 2
■Reference). Then, if an address mark is detected, a data read operation is executed, and if it is not detected, a synchronization field is detected again (see Figure 2 ■).
.

As described above, according to this embodiment, when the sync field is detected by the sync address mark detection circuit 4, the 1-byte elapsed signal k of the byte counter 5 is counted by the control circuit 6 by the number of bytes of the sync field. do. Then, 1 for the number of bytes of the sink field.
When the data input detection signal g of the data shift register 3 does not become active even after counting the byte progress signal k, the sync address mark detection circuit 4 re-detects the sync field. Therefore, even if the first data bit is not input as in the conventional case, a data read operation can be performed without causing a hang-up.

[0016]

According to the floppy disk controller of the present invention, when the sync field is detected by the sync address mark detection circuit, the byte counter counts the number of bytes of read data and generates a 1-byte elapsed signal every 1 byte. This 1-byte elapsed signal is counted by the number of bytes of the sink field by the control circuit. If the data input detection signal from the data shift register does not become active even after counting 1-byte elapsed signals for the number of bytes in the sync field, the sync address mark detection circuit detects the sync field again. conduct. therefore,
When reading data from a floppy disk on which data has been recorded using the single-density recording method in double-density recording mode as in the past, a hang-up may occur even if the first data bit is not input. You can get no floppy disk controller.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a floppy disk controller according to an embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation of a floppy disk controller according to an embodiment of the present invention.

[Explanation of symbols]

1 Data separate circuit 2 Clock shift register 3 Data shift register 4 Clock shift register 5 Byte counter 6 Control circuit a Read data b Window c Separate clock d Separate data e Shift clock f 8-bit parallel data signal g Data input detection signal h 8 bits Parallel clock signal i Pattern match signal (sync/address mark detection signal) k 1-byte elapsed signal

Claims (1)

[Claims] 1. A data separation circuit that receives read data and a window from a floppy disk drive as input and outputs a separate clock, separate data, and a shift clock; and a data separation circuit that receives the separate clock and the shift clock as input, and provides parallel clock signals. a clock shift register that outputs the separate data and the shift clock, and a data shift register that receives the separate data and the shift clock and outputs a parallel data signal and a data input detection signal having the same bits as the clock signal; and the clock signal and the data signal. a sink/address mark detection circuit which takes as an input, detects a sink field and an address mark, and outputs a sink/address mark detection signal, and takes the shift clock as an input and counts the number of bytes of the read data every time one byte elapses. a byte counter that outputs a 1-byte elapsed signal;
a control circuit that receives the sync address mark detection signal, the data input detection signal, and the 1-byte elapsed signal as input, and counts the 1-byte elapsed signal by the number of bytes of the sync field; When the mark detection circuit detects the sync field, the data input detection signal of the data shift register does not become active even if the control circuit counts the 1-byte elapsed signal of the byte counter for the number of bytes of the sync field. In the floppy disk controller, the sync field is re-detected by the sync address mark detection circuit when the sync field is detected.