CDAT4 Front Panel

General Information

Care and Maintenance

Voltage

The CDAT4 accepts 83-240 VAC input. No jumper or switch settings are required.

Air Flow

The CDAT4 has several vent slots located in the bottom cover and in the rear panel, as well as a cooling fan. Proper air flow is very important in order to protect the electronics from damage. When mounting the CDAT4 on a rack, allow at least one inch of clearance for proper ventilation.

On the rear panel of the CDAT4 is a fan filter, which should be checked periodically for debris. If the filter ever becomes clogged, it should be cleaned in the following manner:

1. Pry the filter cover off of the fan assembly.
2. Remove the foam filter element.
3. Place the filter element under running water to remove the debris.
4. Allow the filter element to dry completely. DO NOT PLACE A WET FILTER ELEMENT ON THE INSTRUMENT!
5. Replace the foam filter element and snap the filter cover onto the fan assembly.

Cleaning the Tape Drive

Dust on the tape heads can impair the magnetic media, causing read and write errors. Routine cleaning of the drive heads will prevent this problem from occurring. It is recommended that the tape drive heads be cleaned after approximately 20 hours of actual tape motion (recording, searching, and playback). Use only a qualified DDS DAT cleaning cartridge to perform this task. Employment of any other media cleaning cartridge may damage the drive mechanism.

To clean the tape drive:

1. Insert the cleaning cartridge into the drive (see Loading a Tape). The drive will recognize the cartridge as such.
2. Allow the drive to load and run the tape. Do not press anything during this operation.
3. When tape motion completes, eject the tape.

CDAT4 Tape Format

The CDAT4 accepts computer type DAT/DDS tape cartridges which have the "Medium Recognition System" (NMS) encoding. Most tapes available have this feature, but if in doubt, check with the supplier. Use of 60 meter tapes is not recommended.

Each time a tape is used by the CDAT4, some wear occurs to the tape. Extensive wear to a tape may cause a higher error rate, decreasing the recording speed of the CDAT4. For this reason, a tape should not be re-recorded more than 20 times.

How Data is Recorded to Tape

To understand the tape operation of the CDAT4, it is important to understand some of the terminology used in this manual. This section gives a very brief look at how acquired information is written to tape, and explains the terms used.

The data acquired by the CDAT4 is written to SCSI DAT tape in a particular manner. Figure 2 shows the structure of recorded information on the DAT tape. The following sequence is used when a recording session is initiated:

1. A filemark is written to tape. Filemarks indicate the beginning of a recording session, and are used by the CDAT4 for search operations and during playback.
2. A header is written to tape. The header contains information relevant to the recording session, such as time, date, MPX setting, gain settings, and so on. The header is exactly 128 bytes in length.
3. Data is written to tape.
4. As data is written to tape, index marks are also written at set intervals. Index marks help to split up the data for later search and playback operations, and act as a method of file organization. One index mark is written to tape after every 32,760 samples of data are written.
5. The End of Data (EOD) mark is placed onto tape after a recording session completes. EOD is used to indicate that no more data is present on the tape. If data is later recorded at the end of recorded data, the EOD mark is pushed back.

Operating the CDAT4

Loading a Tape

Wait at least 20 seconds after applying power to the CDAT4 before attempting to load a tape. The instrument must initialize prior to accepting a new DAT tape. Once the machine is initialized, you may load a new tape in the following manner:

1. Insert the tape into the Tape unit cartridge door, ensuring that the arrow on the tape points toward the instrument.
2. Push the cartridge quickly into the cartridge door until the instrument accepts the tape. DO NOT FORCE A TAPE INTO THE INSTRUMENT.

 

After a tape is loaded into the instrument, the CDAT4 will attempt to determine if the tape contains data. This is accomplished by reading a portion of the tape, and then rewinding the tape. This procedure requires a few more seconds than the actual drive load specification.

If a blank tape is detected by the instrument, playback will be inhibited. Conversely, if the tape contains data, record operations are initially disabled. This ensures that the user does not accidentally overwrite previously recorded data.

Menu Operation

The LCD display will display the current menu item. Items displayed will vary according to which mode you are in (see Table 1), as will the functionality of the menu item. For example, in Play mode, the Date menu item will display the date that a played back file was recorded on. In Record, the Date menu item will display the current date.

Table 1 Available Menu Items

To toggle through the various menu items, press the Menu key.

The Mode Menu Item

Record Mode, Play Mode

The CDAT4 has two different modes of operation: play mode and record mode. In play mode, the instrument will allow the user to examine previously recorded data via playback. In record mode, the user may record new data onto tape.

To switch between modes, perform the following operations:

1. Toggle through the menu until the Mode Selection menu item is displayed.
2. Press the Set key. A cursor should appear over the current mode.
3. Use the Up key or Down key to select the appropriate mode.
4. Press the Execute key to activate the mode.

 

Overriding Write Protection

When switching to record mode, the Start key may blink. This is an indication that there is data at the current tape position, and that recording is disabled. This feature helps to ensure that data is not accidentally overwritten.

To override write protection:

1. Toggle through the menu until the Mode Selection menu item is displayed.
2. Press the Set key.
3. Press the Execute key. The Start key should stop blinking.

 

 

The MPX Menu Item

Record Mode, Play Mode

Bandwidth and available recording time is determined by the MPX setting of the CDAT4. Each of the 16 MPX settings have different recording characteristics (see Table 2).

Table 2 Bandwidth Settings

To set the MPX:

1. Switch to record mode.
2. Toggle through the menu until the MPX Selection menu item is displayed.
3. Press the Set key. A cursor should appear over the current MPX setting.
4. Press the Up key or Down key to toggle through the MPX modes.
5. When the appropriate MPX mode is displayed, press the Execute key.

 

 

The Date Menu Item

Record Mode, Play Mode

The Date menu item displays different information based upon which mode the instrument is in. In Record mode, the date displayed on the CDAT4 is the current date. When in Play mode, the date displayed changes to reflect the date of the last file played or searched to.

Setting the Current Date

Record Mode

To set the current date:

1. Switch to Record mode.
2. Toggle through the menu until the Date menu item is displayed.
3. Press the Set key. A cursor should appear over the last digit of the year field.
4. Press the Up key or Down key to increment or decrement the current digit beneath the cursor (respectively). The Left key and Right key are used to toggle between digits in the date.
5. When the correct date is displayed, press the Execute key.

 

 

The Time Menu Item

Record Mode, Play Mode

The Time menu item displays different information based upon which mode the instrument is in. In Record mode, the time displayed on the CDAT4 is the current time. In Play mode, the time displayed reflects the record time of the last file played or searched to.

Setting the Current Time

Record Mode

To set the current time:

1. Switch to record mode.
2. Toggle through the menu until the Time menu item is displayed.
3. Press the Set key. A cursor should appear over the last digit of the time field.
4. Press the Up key or Down key to increment or decrement the current digit beneath the cursor (respectively). The Left key and Right key are used to toggle between digits in the time.
5. When the correct time is displayed, press the Execute key.

 

 

The Gain Menu Item

Record Mode

Gain settings allow for fine tuning of the input full-scale range (see Table 3). The gain setting for each channel should be set to reflect the input voltages. For example, if the input to Channel 1 ranged between -1V and +2V, the gain setting should be ´ 5 for that channel.

Table 3 Full Scale Range Based on Gain

To modify the gain settings:

1. Switch to Record mode.
2. Toggle through the menu until the Gain menu item is displayed.
3. Press the Set key. The gain setting for Channel 1 should appear.
4. Use the Up key and Down key to increment and decrement the gain setting, respectively. Use the Left key or Right key to switch between channels.
5. When the gain settings are correct, press the Execute key.

 

 

The Block Size Menu Item

Record Mode

This menu item controls the number of blocks written to tape during a recording session, as well as the use of the trigger in recording. By setting the block size to any setting other than continuous, the CDAT4 will respond to trigger control for starting the recording session.

Table 4 Block Sizes

To set the Block Size:

1. Switch to Record mode.
2. Toggle through the menu until the Block Size menu item is displayed.
3. Press the Set key. A cursor should appear over the current block size.
4. Use the Up key and Down key to select the block size.
5. When the block size is correct, press the Execute key.

 

The Status Menu Item Record Mode, Play Mode

The Status menu item displays the current state of the SCSI tape unit. Refer to Table 5 for the various messages.

Table 5 Status Messages

The Store Setup Menu Item Record Mode

The Store Setup menu item allows the user to store the current MPX, block size, and gain settings into non-volatile RAM. This allows for the CDAT4 to automatically restore the settings during powerup.

Storing the current setup:

1. Switch to Record mode.
2. Toggle through the menu until the Store Setup menu is displayed.
3. Press the Set key.
4. Press the Execute key. The settings will now be stored.

 

 

The Tape Remaining Menu Item Record Mode

The Tape Remaining menu item provides the user of the CDAT4 with a conservative estimate of the remaining tape capacity. This is displayed only in record mode, and the calculations are performed based upon the current MPX setting.

As mentioned above, the estimates are conservative, generally about 20% less than the actual capacity of the tape.

The Mag Menu Item Record Mode

This menu item displays a peak signal meter. The indicators resemble a bar graph with sixteen linearly increasing levels. These levels are a measure of the peak absolute value during 100 millisecond intervals (spurious peaks may be difficult to discern).

The Play Method Menu Item Play Mode

This menu allows the user to select between the continuous and single play methods. In continuous play, playback will continue until either the user manually stops playback, or the end of data is encountered. In single play, only one file will be played back to the user at a time.

To select the Play Method:

1. Switch to Play mode.
2. Toggle through the menu until the Play Method menu item is displayed.
3. Press the Set key. A cursor should appear over the current play method.
4. Use the Up key or Down key to toggle between the play methods.
5. When the correct play method is displayed, press the Execute key.

 

 

The Search Target Menu Item Play Mode

The Search Target menu item allows a user to choose a particular file and index to search for. Once the target is set by the user, it remains stored until the user modifies it again, or powers down the instrument.

Setting the Search Target
Play Mode

To set the search target:

1. Switch to Play mode.
2. Toggle through the menu until the Search Target menu is displayed.
3. Press the Set key. A cursor should appear on the ones digit of the target file.
4. Use the Left key and Right key to toggle the cursor between the digits of the target. Use the Up key and Down key to increment and decrement the current digit beneath the cursor, respectively. The Set key can be used to toggle between the target file and target index.
5. Once the target file and target index are correctly set, press the Execute key.

 

Executing the Search
Play Mode

To search for the target:

1. Switch to Play mode.
2. Ensure that the target file and target index are correctly set (see above).
3. Press the Search File key.

If EOD is encountered during a search, the file number shown in the menu corresponds to the next file number. For example, if there are seventeen files recorded on the tape (numbered 0-16) and EOD is hit, then file 17 will be displayed.

If a filemark is encountered while searching for an index within a file, then the index after the last will be displayed. For example, if there are 32 indices (numbered 0-31) in file 10, and a search is executed for file 10, index 60, the display will show file 10, index 32 after the search.

The Search EOD Key
Record Mode, Play Mode

The Search EOD key allows a user to quickly position the tape at the end of recorded data. If the tape is not already positioned at the end of data, and the CDAT4 is not performing any motion commands, then the Search EOD key will be active.

To position the tape at the end of recorded data, press the Search EOD key once. When tape motion is completed, the display will show the next file to be recorded. For example, if there are twenty files (numbered 0-19) recorded on the tape, and the user searches to EOD, file number 20 will be displayed to the user on the display. This indicates the number of the next file to be recorded.

The Search Next Key
Play Mode

The Search Next key allows a user to search for the next file on the tape. This search, when executed, will cause the tape to position after the next filemark encountered on tape, and read the header associated with the file. Thus, information such as time, date, and MPX will change to reflect that of the file at the new position.

If the CDAT4 encounters EOD while searching for the next file, the display will show the next file to be recorded, and status will indicate EOD.

NOTE: The Search EOD key is active during playback, but it is not recommended for use. It was initially included to allow the user to skip over the remainder of the file playing back, but some problems may occur in file and index handling (due to the SCSI tape buffer). If this key is used during playback, and there is some question as to the tape positioning, press the Rewind key to correct the problem.

The Rewind Key
Record Mode, Play Mode

The Rewind key allows a user to quickly position the CDAT4 at the beginning of a tape. This key is active when the CDAT4 tape unit is not in motion (recording, searching, or playing) and the tape is not already positioned at the beginning.

NOTE: If there is ever any question as to the actual position of the tape and what is shown on the display, the Rewind key will help to reset the CDAT4 parameters.

The Unload Key
Record Mode, Play Mode

The Unload key is used to eject a tape from the CDAT4. This key is only active when the tape is not performing motion commands (search, play, and record). Pressing this key causes the tape to rewind, and then eject, so the operation may take several seconds.

NOTE: It is recommended that you remove any tape prior to powering down the CDAT4.

Recording Data
Record Mode

Continuous Record Mode vs. Burst Mode

The recording mode used depends upon the block size selected for the session. When the block size is set to continuous, the CDAT4 is prepared to record in Continuous Record Mode. If the block size is set to something other than continuous, then the CDAT4 is prepared to record in Burst Mode.

Continuous Record Mode requires the user to start and stop the recording session manually. The trigger on the CDAT4 is disable in this mode. Files recorded in this mode may be of variable length, depending upon the MPX setting and duration of the recording session.

Burst Mode relies upon the trigger mechanism to initiate recording sessions. The user may opt to use the Manual Trigger on the front of the CDAT4, or connect an external trigger to the Trigger Input. Which trigger method used by the CDAT4 depends upon the position of the Trigger Select switch. When the switch is in the up position, the Manual Trigger initiates the session. When the switch is in the down position, the Trigger Input is used.

Burst Mode records data, as the name implies, in bursts. When a trigger is received by the instrument, data is acquired in files the length of the set block size. Acquisition continues until the block has been acquired. If a continuous trigger is maintained, the instrument will continue recording blocks of data until the trigger is no longer asserted.

There is a special consideration to take into account when recording in burst mode. Prior to accepting trigger input, the file header is written to tape. This allows for quicker response to trigger input, but may result in an empty header when Burst Mode is stopped.

Preparing to Record

1. Connect the inputs to the CDAT4 using BNC type connectors. The input voltages to the CDAT4 should not exceed ± 12V.
2. Switch the CDAT4 to Record Mode.
3. Select the proper gain settings for each input channel.
4. Select the appropriate MPX setting.
5. Select the appropriate Block Size.
6. If Burst Mode is being used with an external trigger, connect the trigger to the Trigger Input BNC and make sure the Trigger Select Switch is in the down position. If Burst Mode is being used with the manual trigger, make sure that the Trigger Select Switch is in the up position.
7. Position the tape such that recording is enabled. If you are recording over existing data, make sure that Write Protection is overridden.

Continuous Record Mode

1. Press the Start key to begin recording.
2. Press the Stop key to stop recording.

Burst Mode with Manual Trigger

1. Press the Start key to prepare for recording.
2. Press the Manual Trigger to record a single burst of data. Hold down the Manual Trigger to record a sequence of bursts.
3. Repeat step 2 for as many bursts as desired.
4. Press the Stop key to stop accepting trigger input. Any bursts being acquired due to the last trigger will continue until the block length is reached.
5. Press the Stop key again.

NOTE: Pressing the Stop key twice before all data from a trigger is acquired will cause the CDAT4 to stop data acquisition immediately. If this is not desired, make sure enough time is allowed between steps 4 and 5 to acquire the remainder of the burst.

Burst Mode with External Trigger

1. Press the Start key to prepare for recording.
2. When a TTL level of 0-5V is received through the Trigger Input, the CDAT4 will record a burst of data. As long as the trigger is sustained, acquisition will continue (in bursts).
3. Press the Stop key to stop accepting trigger input. Any bursts being acquired due to the last trigger will continue until the block length is reached.
4. Press the Stop key again.

NOTE: Pressing the Stop key twice before all data from a trigger is acquired will cause the CDAT4 to stop data acquisition immediately. If this is not desired, make sure enough time is allowed between steps 3 and 4 to acquire the remainder of the burst.

Playing Data
Play Mode

Playing previously recorded data with the CDAT4 is a relatively simple task. The steps below outline the steps involved.

1. Connect the channel output(s) to an appropriate playback device.
2. Switch to Play mode.
3. Select the appropriate Play method.
4. Position the tape at the appropriate file.
5. Press the Start key to begin playback.
6. When finished with playback, press the Stop key. Playback will continue until the playback buffer is emptied. Pressing the Stop key a second time will flush the playback buffer and immediately stop playback.

If the CDAT4 encounters EOD while playing back, it will stop once the file playing is complete. If an EOD is buffered, and the user presses the Stop key once, playback ceases immediately.

Recording Error Correction

Recording Error

During the CDAT4 initialization sequence, a message may appear indicating an error occurred during a recording session. This message appears when a recording session was interrupted by a loss of power prior to writing an EOD mark to tape.

During a recording session, a flag is set indicating that the EOD mark has not yet been written to tape. Since a missing EOD mark may cause numerous problems, the CDAT4 attempts to track the last file and index that were written to tape prior to power loss. If power loss does occur, the flag is stored in non-volatile RAM, and the instrument detects that flag when power is restored.

The CDAT4 stores the last file and index written to tape prior to power loss. A calculation is performed that estimates the amount of data lost in buffers during the session, in order to provide an estimate of where the EOD mark should be placed. The next time the CDAT4 is powered up, the estimated file and index are placed into the search target.

Recovery from a Recording Error

It is important to recover from a recording error immediately, since the missing EOD can cause numerous operating problems. Before correcting the Recording error, make sure that the Search EOD key is not pressed. Searching for a nonexistent EOD mark may confuse the tape drive, causing a long period of tape activity.

1. Switch to Play mode.
2. Toggle through the menu until the Search Target menu item appears.
3. Press the Set key. A file and index number will already appear as a set target. Make note of these numbers, but do not change them.
4. Press the Execute key.
5. Press the Search File key. The CDAT4 will attempt to position itself prior to the area where the EOD mark should have been written.
6. Switch to Record mode. Overriding write protection may be required.
7. Record a dummy file. Once the dummy file is recorded, an EOD mark will be written.

 

CDAT4 Serial Control

Serial Port Parameters

 

The serial port of the CDAT4 operates using the following parameters: 9600 baud, no parity, eight(8) data bits, and one(1) stop bit. Ensure that the computer used to control the CDAT4 has the same operating parameters when attempting to control the instrument.

 

Asserting Serial Control

 

The CDAT4 will only respond to query commands when serial control is not asserted manually by the user. Switching the CDAT4 into serial mode will allow the instrument to respond to commands issued via the serial port, and disable control of the instrument via the front panel. When serial mode is enabled, the user may toggle through the menus of the instrument, but the ability to set the operating parameters is disabled.

 

Turning Serial Control On

1. Toggle through the menu until the Status menu item is displayed.
2. Press the Right key once. An ‘S’ should appear between ‘STATUS’ and ‘FILE’ on the display. The instrument will now accept serial commands.

 

Turning Serial Control Off

1. Toggle through the menu until the Status menu item is displayed.

2. Press the Right key once. The ‘S’ between ‘STATUS’ and ‘FILE’ should disappear from the display. The instrument will stop responding to any command other than a Query command.

 

CDAT4 Serial Commands

 

The CDAT4 has several commands available. See Table 6 for a general listing of the commands. This table describes the purpose of each command, as well as the number of parameters required in the command, the mode(s) in which the command is available, and whether or not serial control must be asserted in order to issue the command to the instrument.

Table 6 Available Serial Commands

Command	Purpose	Parameters	Mode Available	Serial Control
@B	Set Block Size	One (1)	Record	On
@D	Set Date	One (1)	Record	On
@E	Search to End of Data	None (0)	Record, Play	On
@G	Set Gain	Four (4)	Record	On
@M	Set Mode	One (1)	Record, Play	On
@P	Control Playback	One (1)	Play	On
@Q	Query	One (1)	Record, Play	On, Off
@R	Control Recording	One (1)	Record	On
@S	Search for File and Index	Two (2)	Play	On
@T	Set Time	One (1)	Record	On
@W	Rewind Tape	None (0)	Record, Play	On
@X	Set MPX	One (1)	Record	On

 

@B - Set Block Size

 

PURPOSE
The @B command sets the recording block size that the CDAT4 will use.

SYNTAX
@Bx

PARAMETERS
x - [0..5] Corresponds to the block size.

Table 7 Values of Block Sizes

x	Block Size
0	cont
1	32K
2	64K
3	128K
4	256K
5	512K

 

EXAMPLE

@B0 will set the CDAT4 to record continuous blocks.

@D - Set Date

PURPOSE
The @D command sets the date of the CDAT4.

SYNTAX
@Dx

PARAMETERS
x - A string of digits corresponding to the date, in the format of mmddyy.

EXAMPLE
@D081796 will set the CDAT4’s date to 8/17/96.

@E - Search to End of Data

PURPOSE
The @E command positions the tape at the end of recorded data.

SYNTAX
@E

PARAMETERS
None.

EXAMPLE
@E will position the tape at the end of data.

@G - Set Gain

PURPOSE
The @G command sets the gain for each input of the CDAT4.

SYNTAX
@Bw,x,y,z

PARAMETERS
w - [0..6] Corresponds to the gain of input channel 1.
x - [0..6] Corresponds to the gain of input channel 2.
y - [0..6] Corresponds to the gain of input channel 3.
z - [0..6] Corresponds to the gain of input channel 4.

Table 8 Values of Gain Settings

w,x,y,z	Gain Setting
0	´ 1
1	´ 2
2	´ 5
3	´ 10
4	´ 20
5	´ 50
6	´ 100

 

EXAMPLE
@B0,1,2,3 will set the gains as follows: channel 1 ´ 1, channel 2 ´ 2, channel 3 ´ 5, and channel 4 ´ 10.

 

@M - Set Mode

PURPOSE
The @M command sets the mode of the CDAT4.

SYNTAX
@Mx

PARAMETERS
x - 1 to switch to record mode, 0 to switch to play mode.

EXAMPLE
@M1 will set the CDAT4 to record mode.

@P - Control Playback

PURPOSE
The @P command controls playback on the CDAT4.

SYNTAX
@Px

PARAMETERS
x - 1 to start playback, 0 to stop playback.

EXAMPLE
@P1 will cause the CDAT4 to begin playing back data.

@Q - Query CDAT4

PURPOSE
The @Q command queries the CDAT4 for information.

SYNTAX
@Qx

PARAMETERS
x - [0..3] The various query commands available.

Table 9 Available Query Commands

x	Returns
0	File, Index, Mode, Status
1	Date, Time
2	MPX, CH1 gain, CH2 gain, CH3 gain, CH4 gain
3	Remaining tape (in megabytes)

EXAMPLE
@Q0 will query the CDAT4 for the current file, index, mode, and status.

NOTES
The following table gives the meanings of the various status messages.

Table 10 Numeric Status Messages

Returned Status	Meaning
0	WAIT
1	REW
2	BLANK
3	REMOTE
4	SEARCH
5	EOT
6	WPROT
7	EOD
8	RECORD
9	PLAY
10	READY

 

@R - Control Recording

PURPOSE
The @R command controls recording on the CDAT4.

SYNTAX
@Rx

PARAMETERS
x - 1 to start recording, 0 to stop recording.

EXAMPLE
@R1 will cause the CDAT4 to begin recording data.

@S - Search Command

PURPOSE
The @S command searches for a file and index on a tape.

SYNTAX
@Sx,y

PARAMETERS
x - The file to search for.
y - The index to search for.

EXAMPLE
@S1,100 will cause the CDAT4 to search for file 1 and index 100 on the current tape.

@T - Set Time

PURPOSE
The @T command sets the time of the CDAT4.

SYNTAX
@Tx

PARAMETERS
x - A string of digits corresponding to the time, in the format of hhmmss.

EXAMPLE
@D211756 will set the CDAT4’s time to 9:17:56 PM.

@W - Rewind Tape

PURPOSE
The @W command rewinds the tape.

SYNTAX
@W

PARAMETERS
None.

EXAMPLE
@W will rewind the tape in the CDAT4.

@X - Set MPX

PURPOSE
The @X command sets the MPX of the CDAT4.

SYNTAX
@Xx

PARAMETERS
x - [0..15] Set the MPX. 0-7 are MPX modes 0-7, and 8-15 are MPX modes 0A-7A.

EXAMPLE
@X12 will set the CDAT4 MPX mode to 4A.

CDAT4 Example Serial Session

The following is a Serial Session performed using a serial communications package. In this example, the bold items are comments only. CD> refers to information returned by the CDAT4, and US> refers to commands issued by the user.

If you ever use a serial communications package to communicate with the CDAT4, there are several things you can do to make the interface a little more tidy. First, if you can find an option that appends line feeds to carriage returns, set that option. This prevents the terminal program from overwriting data on the screen. Second, set local echo to on. This allows to see what is typed on the screen.

Serial Port Considerations

It is important to note several things pertaining to the serial port of the CDAT4:

1. Commands are case sensitive. All commands begin with a capital letter.
2. Commands are not carried out on the CDAT4 until a carriage return is received by the instrument.
3. Every command returns a status. If the command is successful, a 1 is returned. If a 1 is not returned, the command did not complete successfully.
4. All serial input is ignored by the CDAT4 while commands are being carried out. Commands cannot be issued to the instrument until a status is returned.
5. Ensure that the CDAT4 is in the proper mode (record or play) prior to issuing commands. Commands issued in the wrong mode will fail to execute.
6. When the CDAT4 is toggled in and out of serial mode (by pressing the Right key in the Status menu item), a status is always sent via the serial port. S1 is returned when the CDAT4 is switched into serial mode, and S0 is returned when the CDAT4 is switched out of serial mode.
7. Data returned from the CDAT4 is appended with a carriage return character. For example, a line returned from a Query command actually looks like this:
   4A,0,0,3,3<CR>
8. Commands mimic the actions of the keys on the front panel. For example, sending a stop play (@P0) command acts like pressing the stop button once. Sending the stop play command a second time will flush the playback buffer and stop play immediately.

 

Appendix A - Searching Considerations

When searching for a particular file and index, there are several considerations to take into account:

• If the target file exists, the header of the target file is read, and the tape is positioned after the header.
• If the target file is greater than the number of files on the tape, the unit will position at EOD and display the file number of the next file to record.
• If the target file exists, and the target index exceeds the number of indices in that file, the unit will display the last index in that file, plus one. If the file is the last file recorded on tape, the CDAT4 will position itself at EOD, and display the next file to record.

These considerations are important if you wish to position the tape in such a way to record over existing files.

For example, consider a tape containing 20 files, numbered 0-19. Suppose a user wishes to record over files 15 and on. If the user were to search to file 15, and begin recording, the header of file 15 would still remain on the tape (with no data).

To overcome this problem, the user could search for file 14, and some index number that would exceed the number of indices in that file (30,000 for instance). The CDAT4 would position itself at the end of file 14, and before the header of file 15. If the user were to record at this time, they would successfully overwrite all of file 15, not just the data.

Appendix B - Tape Data Structure

This appendix gives an outline of the data format used by the CDAT4. All information is presented in C style format.

Header Structure

Recorded Data Format

The data recorded consists of groups of signed, 16 bit samples taken at the rate determined by the MPX setting. Each group is composed of a stream of 2 or 4 data samples, optionally combined with an auxiliary sample (for voice and digital channels). Data samples are 2’s complement integers (signed integers), with the least significant byte stored first (Intel 8086 format). Auxiliary samples contain the digital input in the upper byte, and voice input in the lower byte.

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