JPH0259812A - Cd-rom host computer interface device - Google Patents

Abstract

PURPOSE:To decide the end of reproduction of an audio track carried out by a CD-ROM disk reader with the least overhead and to eliminate the deterioration of the data processing ability of a host computer by using the output of a clock signal detecting means as an interruption signal source of the host computer. CONSTITUTION:The output signal SCOMP of a comparator 24 is inputted to a D flip-flop 27 and a D terminal of the fli-flop 27 is pulled up to a power supply VCC. Simultaneously, the acknowledge output signal SACKN received from an SCSI interface circuit 2 is inputted to a CL terminal of the flio-flop 27. Then a Q terminal of the flip-flop 27 is connected to an interruption signal SINTN line of a host computer extension bus via an open collector inverter 28. An interruption signal is transmitted to a host computer 8. Thus it is possible to decide the end of reproduction of an audio track carried out by a CD-ROM disk reader with the least overhead. Then the deterioration of the data processing ability can be avoided for the computer 8.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention relates to a CD-ROM host used in a system that connects a CD-ROM disc reader to a computer and reads data on the disc. Computer interface! Related to jt equipment.

(Prior Art) In recent years, digital audio discs (CDs) in the compact disc format that perform optical reading have rapidly become popular, and computer data can be recorded on the digital audio data channels of these discs. .

CD-ROM (Compact Dlsc-Re
ad 0nly Memory) is a format for recording computer data in the audio data signal area without changing the basic signal format of a digital audio disc for music, and it is a globally unified physical format. It is determined.

That is, as shown in FIG. 3, an audio data area is defined using a subcode frame as a basic unit, one subcode frame (98 audio data frames) is one sector, and one sector is 2352 bytes.

Currently, three types of physical formats for one sector are defined as shown in (1), (2), and (3) in FIG.

Mode 0 can be used as a dummy sector for making the lead-in area and lead-out area of the disc into a CD-ROM JR structure.

In addition, mode 1 and mode 2 are modes in which actual data can be recorded, and the total amount of data that the user can use is 1
If the disk is 60 minutes long, mode 1 will take 540 megabytes and mode 2 will take 630 megabytes.

Data transfer rate is 150 bytes 7sec in mode 1
, 171.1 bytes/sec in mode 2.

Generally speaking, a CD-ROM disk refers to a disk on which code data is recorded in mode 1 format, and the recorded data can be read using a dedicated reading device.

Here, the structure of the mode 1 sector is basically as follows.

■Synchronization pattern for blocking audio data tracks ■Time information/MIN: SEC: FRAME (
SECTOR) ■Mode byte indicating data type (,000QOf)
01) ■ Actual code data (2048 bytes) ■ Error detection/correction code A CD-ROM disk reading device reads data in sectors specified by the host computer from one disk in CD-ROM mode in units of one sector. and is read into the host computer via a CD-ROM host computer interface device.

The CD-ROM disc reading device reads the CD-R,0
In addition to being connected to a host computer by itself via an M host computer interface device, it also conforms to the SCS I standard (Svall Computer System I
one host computer and seven CD-ROM disk readers according to
It can be connected through the 9I bus.

Furthermore, in a CD-ROM disc it is also possible to provide a digital audio track as well as a data track, so that digital audio data can be transmitted to the interface device via a digital audio data bus.

FIG. 5 is a diagram showing the configuration of a CD-ROM disc reading system that reads audio tracks in addition to reading data.

In the figure, a CD-ROM host computer interface device 1 includes a 5C8I interface circuit 2.
, digital-to-analog conversion circuit, and input buffer 4
It consists of

The digital-to-analog conversion circuit 3 includes a D/A converter 5 and a low-pass filter 6. Further, as shown in FIG. 6, the input buffer 4 includes a pull-up resistor 15 for pulling up the pass line, and inverters 16 to 20 as buffers for each signal line.

Here, the CD-ROM host computer interface device 1 is connected to a host computer 8 via a host computer expansion bus 7, and executes a 5C8I bus interface interface procedure under the control of the host computer 8.

Seven CD-ROM disk readers 51 to 57 and C
D-ROM host computer interface device 1
are connected in a daisy chain by SC3I data cables 58-63.

The SC3I bus 9 is connected to terminators 10 and 72 in the CD-ROM host computer interface device 1 and the CD-ROM disk reader 57.
is the terminus.

The devices connected to the SCS I bus 9 are CD-RO
M disk readers 51-57 and CD-ROM host computer interface devices 1 are identified by unique SC3I device IDs assigned to them.

On the other hand, the CD-ROM disk reading devices 51 to 57
to the digital audio data bus 14,
Digital audio data, a synchronization clock signal accompanying the digital audio data, and an analog audio output control signal are sent out.

Further, the CD-ROM disk reading devices 51 to 57 are connected to digital audio interface cables 65 to 71.
Thus, it is connected to the digital/analog conversion circuit 3 in a daisy chain manner, and is terminated by terminators 13 and 73 similarly to the 5C3I bus 9.

The output of low-pass filter 6 is supplied to amplifiers 29 and 30 to drive speakers 31 and 32.

The digital audio data bus 14 then outputs digital audio data S DATAN and a pit clock signal S that accompanies the digital audio data.
BCKLN, sample clock signal 5LRCKN
, the muting signal SMUTEN, and the de-emphasis signal SEMPIIN are transmitted in negative logic at the timing shown in FIG. 7, and are logically inverted by the input buffer 4. Logically inverted signal S DATASS BCLK
and S LRCK are supplied to the D/A converter 5,
Digital data is converted to an analog signal. Then, unnecessary bands of this analog signal are cut by a low-pass filter 6, and analog audio signals SAL and SAR are generated.
is output as

Further, the muting signal A MUTE and the de-emphasis on/off signal S EXPH are supplied to the low pass filter 6 to perform the following control.

(2) SMUTE is a signal for muting on/off control of analog audio output signals.

S MUTE--"LO level": Muting on S MUTE--"Hl level 2: Muting on
OFF ■S EMPH is a signal for controlling de-emphasis on/off of analog audio signal output.

SEMPI+-"LO level": De-emphasis on SEMPI+-"HI level": De-emphasis off Here, the host computer 8 selects the CD-ROM disk reader 56 according to the interface procedure shown in FIG. CDs other than CD-ROM reader 56
- The ROM reading device shall be in a state in which it is released from the 5C3I bus 9.

Furthermore, it is assumed that all devices are in a state of being released from the digital audio data bus 14, and that the digital audio data bus 14 is in a bus-free state. Therefore, the inputs of the input buffer 4 are terminated by the power supply side pull-up terminator 15, and are all at "Hl level 2."

In this state, the analog audio output signals SAL and SAI? is muted and de-emphasis is turned off.

The host computer 8 sends commands for playing audio tracks on the CD-ROM disc to the CD-ROM disc.
If you specify the section of the digital audio track to be transferred to the disc reading device 56 and played, the CD-RO
M host computer interface device 1 and CD
- The digital audio bus 14 with the ROM disk reading device 56 is connected, and audio tracks can be played back.

The 5C8I commands that support playback of audio tracks are variously defined by manufacturers as 10-byte group 6 commands, as shown in FIG. 9, and are called pengu unique commands.

The basic format of the command is shown in FIG. For command codes COh and C1h, bytes 02-0 as shown in Figures 11 and 12.
Logical block address or subcode address (absolute time, track number) in parameter field 5.
In the case of command code C2h, all 4 bytes are set to zero. Also, the LINK bit of byte 09 (
Bit 0) has the following meaning depending on its value.

- Linkml: Indicates whether it is a single command or the final command in a series of linked commands.

- Link=0: Indicates whether the command is linked.

The Flag bit is valid only when the Link bit is set, and after the link-specified command is successfully completed, the CD-ROM disk reader will transmit a message such as the one below to the host computer.

・Flag-0: ”LINKED COM
MAND COMPLETE”・Flag-1:
“LINKBD COMMAND COMPLETE
In response to the WITHFLAG""ST I LL" command (code C2h), the audio track playback is temporarily interrupted and the 5TILL operation is performed with the subcode lower address that was played immediately before this command being issued as the target address. S M
By setting the UTE to the "LO level", muting is turned on and the search for the same subcode low address is continued. In the 5TILL operation, the occupation of the digital audio data bus is not released.

5TIL by issuing “PLAY AUDIO” command.
The L state is released and audio track playback starts from the subcode Q address position stored immediately before the start of the ST I LL operation.

On the host computer 8 side, if a CD-ROM disk reader is performing audio playback, the SC8I device ID is held in the status register of the operating system or application program, and all CD-ROM disk readers are If the playback is not executed, the previous gQ CD-ROM
SC of host computer interface device 1 itself
5I device ID is retained.

As an example of the operation, after the search for track number 3 is completed, L
/R-ch A case will be described in which stereo playback is started and played to the end of track number 7.

The host computer 8 is the scs shown in FIG.
Figures 13 and 14 according to the r bus interface procedure.
The commands shown in the figure are transferred in this order to the CD-ROM disc reader 56 in linked form or singly.

FIG. 13 shows the "AUDIOTRACK 5EARCH" command, and bit 1 (PLAY bit) of byte 1 specifies the playback mode. By setting this to 1, the performance is automatically started from the address specified by bytes 2 to 5 after the search is completed. This PLAY
If the bit is set to 0, the pause operation will begin after the search is complete.

Bits 7 to 6 (TYPE) of byte 9 specify the address representation method. Setting this to 10 instructs to search by track number. Note that setting OO instructs to search by logical block address. Also, if you set 01, the absolute time specified by the CD standard (formerly N:SEC:FRAMIE
) instructs to search.

Figure 14 shows the “Play Audio” command,
Bits 2 to 0 of byte 1 specify the playback mode of the audio track. By setting 011 in this field, it is instructed to reproduce in L/R-ch stereo until the performance end address specified by bytes 2 to 5. Bits 7-6 of byte 9 are “Audio Track”.
5search” command, indicating that the address expression is a track number.

After the host computer 8 confirms that the CD-ROM reader 56 has completed the single or link command execution, the host computer 8 stores the C in the device ID holding status register (not shown).
Set the 5C5I device ID of the D-ROM disk reader 56.

With the above command, the CD-ROM disk reading device 56 reads PMIN"PSEC in the data of subcode Q stored in the TOC area read before starting the search.
The start and final absolute addresses of the track with the specified number are calculated based on the "and PFRAM" data, and the search for track number 3 is started.

S EMPH is “C0NT” of the subcode Q data.
C0NTl?0L-OX
If it is OOTE, it is de-emphasis off and C0NT.
If R0L-OXOI is present, de-emphasis is on. The S EMPH state switch is performed during a preceding pause period of at least two seconds in the audio data track to be played.

When the search for the target track number 3 is completed, during the preceding pause period in track 3, set the state of the 5EXPN line according to the emphasis mode indicated by C0NTR0I, and play in L/R-ch stereo playback mode. Start playing the audio track and
A digital audio data bus 14 is acquired and digital audio data and an accompanying synchronized clock signal are transmitted onto the audio data bus.

Furthermore, the mute release of the analog output is instructed as SMUTEN-'LO level 2. Even if the CD-ROM disk reading device 56, which is currently playing an audio track, is released from the SC8I bus 50 in response to an instruction from the host computer 8, the digital audio data bus 14 is not released.

The CD-ROM disk reproducing device 56 uses the relative address “old N” SEC” “FRAME” in the subcode Q data.
” and the absolute address “AlN” ASEC” “8FRAME
”, the final address of the track to be played is detected, and when the audio data playback at the address is completed, the muting signal S MUTEN is set to “Hl”.
level", the low-pass filter 6 in the CD-ROM host computer interface device 8 is instructed to mute the analog audio signal outputs SAL and SAR.

Then, to release the CD-ROM disc reader 56 from the digital audio data bus 14, the signals S DATAN,
S BCLKN , S LRCKN and S EM
PHN is changed from "LO level" to "HI level".

Note that the host computer 8 sends a "READ" command to the CD-ROM disk reading device 56 as shown in FIG.
5UBCODE-Q DATA & PLAYING
5TATUS" command (code C6h), the CD-ROM disc reader 56:
The status data in the format shown in FIG. 15 is transferred by the number of transfer bytes specified by byte 1 of the command shown in FIG. 16 from byte 0. The host computer 8 can determine the end of playback by checking byte 0 (performance status byte) of the returned status data.

The performance statuses are assigned as follows.

-00h: 'AUDIOTRACK 5EAR
While playing the audio track after executing the CII' (PLAY bit-1) command or the “PLAY AIJDIO” command ・Olh 2 After executing the “ST I LL” command “
5TILL° in operation・02h: “AUDIOTRACK 5EARCII
” (PLAY bit-1) “PA” after command execution
USE” in operation / 03h Nio-Dorac performance end status After determining the end of deaf playback, the CD-ROM is stored in the device ID holding register.
SC3I of host computer interface device 1
Device ID is set.

If the audio data bus becomes bus-free and the 5C3I device ID of the CD-ROM host computer interface device 1 is set in the device ID holding register, another CD-ROM disk reading device can access the digital audio data bus 14. You can play audio tracks by acquiring .

The host computer 8 sends a 5C3I command for audio playback according to a predetermined SC3I path interface procedure to a CD that is requested by the operating system or application program of the host computer 8.
- Start playing the audio tracks in the above-mentioned order by transferring to the ROM reading device.

(Problems to be Solved by the Invention) By the way, when a CD-ROM host computer interface device as described above is used in a system that requires bus arbitration, and one CD-ROM disk reading device is used to play back an audio track, If the host computer processes the computer data read by the other CD-ROM disk reader, the following problems will occur.

That is, in order to check the playback status of a CD-ROM disk reader that is playing back an audio track even when the host computer is processing data, the host computer sends the "READ" signal according to the 5C3I bus sequence shown in FIG.
5UBCODE-Q DATA & PLAYING
5TATUS'' command must be issued periodically, but the SC3I pass sequence requires a large amount of time (hereinafter referred to as overhead) to obtain the desired data, and the data processing capacity of the host computer while playing the audio track is limited. is significantly reduced.

The present invention has been made in consideration of the above circumstances, and is used in a system that requires path arbitration. The purpose of this is to prevent the data processing ability of the host computer from decreasing even when the computer data read by the reading device is processed by the host computer.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve this object, the present invention has a plurality of CD-RO
digital audio data output from the M disk reader through a digital audio data bus;
input interface means for respectively inputting a synchronous clock signal and an analog audio output control signal accompanying this data; digital/analog conversion means for converting input digital audio data into an analog audio signal; and said digital audio data bus. The apparatus includes a synchronous clock signal detecting means for identifying the presence or absence of the above-mentioned synchronous clock signal, and a signal transmitting means for transmitting an output signal of the synchronous clock signal detecting means to a host computer.

(Function) In the CD-ROM host computer interface device of this embodiment, the output of the clock signal detection means can be used as the interrupt signal source of the host computer, so the host computer can use the 5C5I, which has a large overhead.
“READ 5UBCODE-” according to the path sequence
CD with minimal overhead without issuing Q DATA & PLAYING 5TATUS” commands.
- It is possible to determine the end of the audio track playback of a ROM disc reader, and the execution time of a routine in processing data from another CD-ROM disc reader that is running during audio track playback is not reduced.

(Example) Hereinafter, details of an example of the present invention will be described based on the drawings.

FIG. 1 is a diagram showing the configuration of an embodiment of a CD-ROM host computer interface of the present invention, and parts common to FIGS. 5 and 6 are given the same reference numerals.

In the figure, a CD-ROM host computer interface device 1 includes an SC5I interface circuit 2.
, a digital-to-analog conversion circuit 3, and an input buffer 4.

The digital-to-analog conversion circuit 3 includes a D/A converter 5
and a low-pass filter 6. The input buffer 4 also includes a pull-up resistor 15 for pulling up the pass line, and an inverter 1 as a buffer for each signal line.
6 to 20.

In the figure, 11 and 12 are SC5I interface connectors, and 13 is a digital audio interface connector.

Further, 21 is an inverter, 22 and 23 are resistors and capacitors that constitute a robust filter, 24 is a comparator, and 25 and 26 are bases. i Resistance where lightning voltage is generated, 27
is a D flip-flop, and 28 is an inverter of the oven collector.

The CD-ROM host computer interface device 1 of this embodiment is connected to a host computer 8 via a host computer expansion bus 7, and executes a 5C8I bus interface interface procedure under the control of the host computer 8.

In this embodiment, the sample clock signal S L via the digital audio interface connector 13
The RCKN line is inverted by the buffer 18 and becomes a positive logic signal S_LRCK. This SL RCK is further buffered by an inverter 21, and a resistor 2
2 and a capacitor 23. The cutoff frequency of this low-pass filter is the sample clock signal S Ll? The frequency is set sufficiently lower than the frequency of CKN.

The low-pass filter converts the rectangular wave sample clock signal S_LRCK with a duty of 50% into a DC voltage signal S_LPP. This DC voltage signal S
LPI' is set to the reference voltage VRE P by the comparator 24.
compared to This base voltage V REP is generated by the resistor 25 and the resistor 26, and the resistor 25 and the resistor 26
By setting the ratio of the resistance value to 3=7, the reference voltage VREF=0.7×Vcc. And the DC voltage signal 5LP of the low-pass filter
The clock signal is detected depending on whether F is greater than or equal to the reference voltage V REF.

The output signal S COMP of the comparator 24 is input to the clock terminal of the D flip-flop 27.

The D terminal of the D flip-flop 27 is pulled up to the power supply vCC, and the acknowledge output signal 5ACKN from the SC5I interface circuit 2 is input to the CL terminal. Furthermore, the Q terminal of the D flip-flop 27 is connected to the interrupt signal 5INTN line of the host computer expansion bus through the oven collector inverter 28, and the interrupt signal is transmitted to the host computer 8.

Next, the operation of the CD-ROM host computer interface device 1 of this embodiment when the digital audio data bus is occupied and released will be explained.

The host computer 8 issues the "AUDIOTRACK 5EARC11" command (code C0h) and the "AUDIOPLAY" command (code C0h) to the CD-ROM disc reader 56 according to the 5C8I interface procedure.
Issue code C1h) alone or in linked form,
Assume that L/R-2Ch stereo reproduction is instructed from track number 3 to the final audio track of track number 7.

FIG. 2 shows changes in the signal state of each signal line of the digital audio data bus 14.

When the search for the specified audio track is complete,
Before the D-ROM disk reader 56 sends digital audio data, its accompanying synchronized clock signal, and analog audio output control signals onto the digital audio data bus 14, each line of the digital audio data bus 14 is connected to " Since the sample clock signal is at the Hl level and there is no sample clock signal, the DC voltage signal S LPF output from the low-pass filter is equal to VCC. Therefore, the output of the comparator 24 is at the Hl level.

The D-flip-flop 27 to which the output of the comparator 24 is supplied is set to "PLAY AUDIO" by the signal SACKN output from the 5C3I interface circuit 2.
"Cleared before the command is forwarded.

By sending digital audio data to the digital audio data bus 14, the sample clock line of the digital audio data bus 14 is
, IHH2, and a rectangular wave with a duty of 50% is transmitted, so the DC voltage output signal S LP of the low-pass filter
F is 0.5Vcc.

Furthermore, since S LPP < VREP, the output S COMP of the comparator 24 changes to the "LO level".

While the audio track is being played back, S COMP-"LO level" is held.

The CD-ROM disk reproducing device 56 reads the relative address (“old N” SEC” “FR”) in the subcode Q data.
AME'), m vs. 7 tres ("AMIN""ASEC"
AFl? The final address of the track to be played is detected, and when the playback of the audio data at this address is completed, the muting signal 5HOTEN is raised to the "Hll level" and the CD-ROM host computer The low-pass filter 6 in the interface device 8 is instructed to mute the analog audio signal outputs SAL and SAR, and the digital audio data bus 14 is released.

By releasing the digital audio data bus 14, all signal lines including the sample clock line change to the "Hl level", that is, Vcc, so that the DC voltage output signal S LPF of the low-pass filter is 0.5.
Changes from Vcc to Vcc.

Then, when S LPF≧V REF, the output of the comparator 24 changes from the "LO level" to the "Hll level".As a result, the Q of the flop 27 during the D flip changes.
The terminal output changes from "LO level" to "H level". Therefore, the interrupt signal 5INTN, which is the output of the oven collector inverter 28, changes from "Hl level" to "LO level".
The level changes to '', and an interrupt is generated to the host computer 8.

Immediately after the process currently being executed is completed, the host computer 8 sends the negative polarity pulse SACKN to the D flip.
It is output to the clear terminal CL of the flop 27 and clears the D flip Φ flop 27.

Furthermore, after executing the interrupt process necessary to complete the playback of the audio track, such as setting the SCSI device ID of the CD-ROM host computer interface device 1 in the device ID holding register, the process returns to the process before the interrupt.

Thus, according to this embodiment, the output of the clock signal detection circuit can be used as the interrupt signal source of the host computer 8, so the host computer 8 can use the SC5I interface 2 circuit, which has a large overhead, as an interrupt signal source.
Follow the I-pass interface 14 steps to “READ 5U”
BCODE-Q DATA & PLAYING 5TA
There is no need to issue TUS' commands periodically.

As a result, it is possible to determine the end of audio track playback on a CD-ROM disc reader with minimal overhead, and to process data read from another CD-ROM disc reader while the audio track is being played. The decrease in routine execution time can be suppressed.

[Effects of the Invention] As explained above, in the CD-ROM host computer interface device of the present invention, the output of the clock signal detection means can be used as the interrupt signal source of the host computer, so the host computer can use the SCS I, which has a large overhead. “REA” according to the path sequence
D 5UBCODE-Q DATA & PLAYING
CD-R without issuing the STATUS command.
The end of playback of the audio track of the OM disc reader can be determined.

Therefore, even when used in a system requiring bus arbitration, the data processing ability of the host computer does not deteriorate.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention, FIG. 2 is a waveform diagram for explaining the operation of the device of the embodiment, and FIG. 3 is a C
Figure 4 is a diagram showing the physical structure of the digital audio data channel and subcode channel of CD-R.
A diagram showing the sector structure of an OM mode 1 disk, FIG.
FIG. 6 is a diagram showing the configuration of a conventional CD-ROM host computer interface device, FIG. 7 is a diagram showing signal waveforms on the digital audio data bus, and FIG. 8 is a diagram showing the configuration of a conventional CD-ROM host computer interface device.
Figure 9 shows the C3I bus interface procedure.
A diagram showing a list of C5I group 6 commands, FIG. 10 is a diagram showing the format of SC3I group 6 commands,
Figure 11 shows the format of the "AUDIOTRACK 5EARCH" command, and Figure 12 shows the format of the "PLAY
Figures 13 and 14 show the format of the "ALIDIO" command. ＾CK 5
EAI? C11” command and “PLAY AUDI”
Figure 15 shows an example of the “RE” command byte.
AD 5UBCODE-Q DATA & PLAYI
FIG. 16 is a diagram showing the format of the "NG 5TATUS" command. FIG. 16 is a diagram showing the format of the status byte. 1...CD-ROM host computer interface device, 2...SC5I interface circuit, 3.
...Digital analog conversion circuit, 4...Input buffer, 5...D/A converter, 6...Low pass filter, 7...Host computer expansion bus, 8...
-Host computer, 9...SC5I bus, 11.
12...SC3I interface connector, 13.
・・Digital audio interface connector,
15... Pull-up resistor, 16-21... Inverter, 22, 25.26... Resistor, 23... Capacitor, 24... Comparator, 27... D-flip-flop, 28...・Oven collector inverter. Applicant: Toshiba Corporation

Claims (1)

[Claims] (1) Input interface means for respectively inputting digital audio data outputted from a plurality of CD-ROM disk reading devices through a digital audio data bus, a synchronization clock signal accompanying this data, and an analog audio output control signal; digital/analog conversion means for converting digital audio data into analog audio signals; synchronous clock signal detection means for identifying the presence or absence of the synchronous clock signal on the digital audio data bus; and the synchronous clock signal detection means. 1. A CD-ROM host computer interface device comprising: signal transmission means for transmitting an output signal of the CD-ROM to a host computer.