Das Oszi Protocol

The Hantek DSO5xxxB (aka Das_Oszi Project) series oscilloscopes, rebadged under various other names, have a USB interface intended for communicating with software running on a PC. A proprietary protocol is used by the Hantek Windows software. This page documents that protocol.

Hantek provides the TTScope software, which is for Windows only. No SDK is available for any platform.

Credits

 * The initial import of this documentation comes from the work "tinhead" has done over on the www.mikrocontroller.net pages.

Introduction
The DSOs are identifiable only by the USB VID:PID 049f:505a (this VID is actually assigned to Compaq), and the bus and device address. When operating several DSO5xxxBs on a PC they cannot be distinguished by their serial number as Hantek sets the iSerial field in the USB descriptor to 0.

The CPU is the MIZI Research/Samsung S3C2410 SMDK. It contains the USB char driver (usb-char.c, Linux 2.4.18), and which uses the VID:PID 049f:505a. Although the DSO is based on a newer kernel (2.6.13), this driver was taken from the previous model Tekway DST1000 (not B!).

Apparently the DSO5xxxBM/BMV models, running Linux 2.6.30.4, use the "serial gadget" driver. Whether this is an improvement is currently not known.

Another effect of this driver is that the DSO briefly shows up at boot with another VID:PID on the USB bus. The bootloader (vivi) uses a SoC monitor, such as the Samsung S3C2440 SMDK (u2440mon), which when booting reports its own VID:PID on the USB port. While this may be very useful for hacking, backup or similar, changing the VID:PID causes BSODs on Win64 PCs.

The protocol uses USB bulk transfers (outbound endpoint 1, inbound endpoint 2) with a maximum packet size of 64 bytes. DSO protocol messages longer than 64 bytes are split up over several bulk packets.

Hantek's DSO protocol is layered directly on top of the USB bulk transfers. It is request/response oriented, meaning the USB host sends a request and receives a list of answers. The protocol can therefore be used in a single-threaded application using synchronous USB communication, even though Hantek's TTScope application uses separate transmit and receive threads.

Basic Structure
The message format is the same for requests and responses. Each message begins with a marker byte. There are two different markers:


 * 0x53: normal message
 * 0x43: debug message

This is followed by two bytes indicating the length of the message, LSB first, excluding the marker and length fields.

The word length is followed by the command byte. The reply to this command will have bit 7 set in the command byte. Therefore command bytes from PC to device are always smaller than 0x80, and the responses are always greater than or equal to 0x80.

The command byte is followed by command-specific data bytes. Some commands use the first data byte as a sub-command. The number of data bytes can be zero.

The data byte is followed by a primitive checksum byte. To calculate this checksum, add up all the bytes of the message. The LSB of this sum is used as the checksum.

0x53 Normal messages
Most 0x53 messages are used by the TTScope software.

0x00 Echo
All data bytes in the request are simply returned unchanged.

0x01 Read DSO settings
This gives a long record in which the current settings of the DSO are binary encoded.

The request:

The reply contains the DSO settings (SYSData):

Details of the SYSData format can be found at http://www.mikrocontroller.net/articles/Datei:SysDATA_v1.0.zip

To ensure that the SYSData structure is decoded correctly it is recommended to read the /protocol.inf file immediately after connecting (see Read file).

If the protocol.inf file on the DSO is not readable or available the reply will be empty, i.e. it will contain no data byte:

0x02 Read sample data
Only the sample data of the two channels (CH1/CH2) can be retrieved. The REF, MATH and FFT data can not be accessed, which is probably why Hantek's TTScope software shows nonsense data under "PowerSpectrum" and "WaveTabulator".

The request:

The DSO responds with at least 3 and at most 202 packets. The first packet (subcommand 0x00) describes the total length of the sample data. The second packet (subcommand 0x01) contains a channel number and the sample data itself. If the sample data is longer than 10000 bytes, further packets with subcommand 0x01 are sent.

This is an example of a small transfer from a DSO5xxxB set to 4ns/DIV and 4K buffer:

Here's an example with more data (150 packets with 10000 sample bytes per packet) from a DSO1202BV with 2ms/DIV and 2M buffer:

If an errors occurs during transmission, a special packet is sent with subcommand 0x03. This can also be sent if the DSO is in STOP mode, in which case there is no data available.

Since the sample data contains no information about the current DSO settings (channel, volts/DIV, timebase), it is important to read the settings first. The following commands ensure a consistency data set:


 * 0x12 Lock panel
 * 0x01 Read DSO settings
 * 0x12 Unlock panel
 * 0x02 Read sample data
 * 0x00 or 0x01 can be used as "idle" commands

If both channels need to be read, the samples can be read sequentially:


 * 0x12 Lock panel
 * 0x01 Read DSO settings
 * 0x12 Unlock panel
 * 0x02 Read CH1 sample data
 * 0x02 Read CH2 sample data
 * 0x00 or 0x01 can be used as "idle" commands

Originally (in the Tekway DST1000 with 2.5Kpoint memory) the panel was also locked during the sample data transmission. This is not recommended for the current DSOs, since the data volumes are much higher than in this original model.

The sample data are post-processed from the image memory. The values are 10 DIV vertical (-127 to 127) and 20 DIV horizontal.

If the window timebase is smaller than the main timebase, only the visible part of the data is transmitted (see http://www.mikrocontroller.net/topic/205820?page=4#2613537).

0x10 Read file
This function can be used to read any file on the DSO, but is primarily intended to read the protocol.inf (see Read DSO settings) and keyprotocol.inf (see Keypress trigger) files.

The request must include the complete file path.

The response uses two subcommands:


 * 0x01: Data
 * 0x02: Checksum of all data

If the contents of the file don't fit in one response packet, further packets with the subcommand 0x01 are sent. The packet with subcommand 0x02 marks the end of the file transfer, and contains a checksum of the entire file.

0x11 Write DSO settings
To write settings, the data format specified in Read DSO settings must be used:

The response contains a status byte, where 0x00 denotes success and anything else is an error:

0x12 Lock/unlock control panel, start/stop acquisition
Lets you start/stop DSO acquisition (subcommand 0x00) or lock/unlock the DSO's front panel controls (subcommand 0x01).

Start DSO acquisition:

Stop DSO acquisition:

The response contains the sent start/stop command:

As far as we know the "start/stop DSO acquisition" function triggers the same action internally as pressing the "run stop" button on the control panel. However it appears to be somewhat buggy. Call this function before retrieving sample data from the DSO.

Lock control panel:

Unlock control panel:

When the control panel is locked a red key appears on the top status bar of the DSO's display, and the controls no longer respond.

The response contains the sent lock/unlock command:

0x13 Keypress trigger
Lets you simulate the press of nearly any button on the DSO's control panel. The desired key is selected by two bytes of data:

The first byte is the key code. The second byte is the number of key presses, according to Hantek. However values higher than one appear to result in only one keypress regardless, so there is no point is specifying anything other than 0x01 for this.

The following keycodes are available for the Hantek DSO5xxxB/BM/BMV, Tekway DST1xxxB and Voltcraft DSO-3062C bench scopes:

0x00 0x01 - F0 0x01 0x01 - F1 0x02 0x01 - F2 0x03 0x01 - F3 0x04 0x01 - F4 0x05 0x01 - F5 0x06 0x01 - F6 0x07 0x01 - F7 0x08 0x01 - V0 left turn 0x09 0x01 - V0 right turn 0x0A 0x01 - V0 press 0x0B 0x01 - Save/Recall 0x0C 0x01 - Measure 0x0D 0x01 - Acquire 0x0E 0x01 - Utility 0x0F 0x01 - Cursor 0x10 0x01 - Display 0x11 0x01 - Autoset 0x12 0x01 - Single Seq Taste 0x13 0x01 - Run/Stop 0x14 0x01 - Help 0x15 0x01 - Default Setup 0x16 0x01 - Save to USB 0x17 0x01 - Math Menu 0x18 0x01 - CH1 Menu 0x19 0x01 - CH1 Position left turn 0x1A 0x01 - CH1 Position right turn 0x1B 0x01 - CH1 Position press 0x1C 0x01 - CH1 Volts/Div left turn 0x1D 0x01 - Ch1 Volts/Div right turn 0x1E 0x01 - CH2 Menu 0x1F 0x01 - CH2 Position left turn 0x20 0x01 - CH2 Position right turn 0x21 0x01 - CH2 Position press 0x22 0x01 - CH2 Volts/Div left turn 0x23 0x01 - Ch2 Volts/Div right turn 0x24 0x01 - Horz Menu 0x25 0x01 - Horizontal Position right turn 0x26 0x01 - Horizontal Position left turn 0x27 0x01 - Horizontal Position press 0x28 0x01 - Horizontal Sec/Div left turn 0x29 0x01 - Horizontal Sec/Div right turn 0x2A 0x01 - Trig Menu 0x2B 0x01 - Trigger Level left turn 0x2C 0x01 - Trigger Level right turn 0x2D 0x01 - Trigger Level press 0x2E 0x01 - Set to 50% 0x2F 0x01 - Force Trig 0x30 0x01 - Probe Check

The following keycodes are available for the Hantek DSO1xxxB/BV handheld scopes:

0x00 0x01 - Fx NULL 0x01 0x01 - Menu on/Off 0x02 0x01 - F1 0x03 0x01 - F2 0x04 0x01 - F3 0x05 0x01 - F4 0x06 0x01 - F5 0x07 0x01 - DMM V 0x08 0x01 - DMM A 0x09 0x01 - DMM Ohm 0x0A 0x01 - DMM Diode 0x0B 0x01 - DMM Continuity 0x0C 0x01 - DMM Capacitance 0x0D 0x01 - DMM/DSO switch 0x0E 0x01 - Save/Recall 0x0F 0x01 - Measure 0x10 0x01 - Utility 0x11 0x01 - Cursor 0x12 0x01 - CH1 Menu 0x13 0x01 - Math Menu 0x14 0x01 - CH2 Menu 0x15 0x01 - Default Setup 0x16 0x01 - Save to USB 0x17 0x01 - Math Menu 0x18 0x01 - CH1 Volts/Div + 0x19 0x01 - CH1 Volts/Div - 0x1A 0x01 - CH1 Position + 0x1B 0x01 - CH1 Position - 0x1C 0x01 - CH2 Position + 0x1D 0x01 - CH2 Position - 0x1E 0x01 - CH2 Volts/Div + 0x1F 0x01 - CH2 Volts/Div - 0x20 0x01 - Horizontal Sec/Div - 0x21 0x01 - Horizontal Sec/Div + 0x22 0x01 - Horizontal Position + 0x23 0x01 - Horizontal Position - 0x24 0x01 - Trigger Level + 0x25 0x01 - Trigger Level - 0x26 0x01 - Run/Stop 0x27 0x01 - Autoset 0x28 0x01 - Multifunktion Enter 0x29 0x01 - Multifunktion Up 0x2A 0x01 - Multifunktion Down 0x2B 0x01 - Multifunktion Left 0x2C 0x01 - Multifunktion Right

To make sure keycodes are valid on the DSO, you should read the /keyprotocol.inf immediately after connecting (see Read file).

The keyprotocol.inf file is structured as follows:
 * the first line represents the number of key codes
 * the second line marks the beginning of the list
 * the following lines contain the key name as used by the firmware, followed by the number of bytes used for each key code
 * the last line marks the end of the list

The line number after [START] - 1 corresponds to that key's keycode. This is the keyprotocol.inf file for a Hantek DSO5202B:

[TOTAL] 49 [START] [FN-0-KEY] 1 [FN-1-KEY] 1 [FN-2-KEY] 1 [FN-3-KEY] 1 [FN-4-KEY] 1 [FN-5-KEY] 1 [FN-6-KEY] 1 [FN-7-KEY] 1 [FN-MLEFT-KEY] 1 [FN-MRIGHT-KEY] 1 [FN-MZERO-KEY] 1 [MENU-SR-KEY] 1 [MENU-MEASURE-KEY] 1 [MENU-ACQUIRE-KEY] 1 [MENU-UTILITY-KEY] 1 [MENU-CURSOR-KEY] 1 [MENU-DISPLAY-KEY] 1 [CT-AUTOSET-KEY] 1 [CT-SINGLESEQ-KEY] 1 [CT-RS-KEY] 1 [CT-HELP-KEY] 1 [CT-DS-KEY] 1 [CT-STU-KEY] 1 [VT-MATH-MENU-KEY] 1 [VT-CH1-MENU-KEY] 1 [VT-CH1-PSUB-KEY] 1 [VT-CH1-PADD-KEY] 1 [VT-CH1-PZERO-KEY] 1 [VT-CH1-VBSUB-KEY] 1 [VT-CH1-VBADD-KEY] 1 [VT-CH2-MENU-KEY] 1 [VT-CH2-PSUB-KEY] 1 [VT-CH2-PADD-KEY] 1 [VT-CH2-PZERO-KEY] 1 [VT-CH2-VBSUB-KEY] 1 [VT-CH2-VBADD-KEY] 1 [HZ-MENU-KEY] 1 [HZ-PSUB-KEY] 1 [HZ-PADD-KEY] 1 [HZ-PZERO-KEY] 1 [HZ-TBSUB-KEY] 1 [HZ-TBADD-KEY] 1 [TG-MENU-KEY] 1 [TG-PSUB-KEY] 1 [TG-PADD-KEY] 1 [TG-PZERO-KEY] 1 [TG-PHALF-KEY] 1 [TG-FORCE-KEY] 1 [TG-PROBECHECK-KEY] 1 [END]

The reply to a key command contains a data byte that refers to the menu that was displayed in response to the keypress. The menu need not actually be displayed.

0x14 Set system time
Lets you set the system time.

The data bytes:


 * Byte 1: Year (LSB)
 * Byte 2: Year (MSB)
 * Byte 3: Month (1...12)
 * Byte 4: Day (1...31)
 * Byte 5: Hour (0...23)
 * Byte 6: Minute (0...59)
 * Byte 7: Second (0...59)

The reply is a packet without data bytes:

0x20 Screenshot
After receiving this command, the DSO sends a screenshot image without size or color palette information. It is sent back in multiple reply messages, up to a total of 384000 bytes. This corresponds to the 800x480 resolution of the display, with a color depth of 8 bits.

The PC sends a request without data bytes:

The DSO responds with 37 packets of 10208 bytes, with subcommand 0x01. The 38th packet is a little shorter, containing only 6304 bytes. After this another packet is sent with subcommand 0x02, containing a primitive checksum.

These DSO protocol packets are split up into multiple USB packets, but your USB library should resolve this transparently.

The received image is in the format of a windows bitmap with 256 colors. The image is flipped vertically, i.e. the bottom line is sent first. The color palette is compiled into the  program on the DSO, and TTScope on the PC, and has a length of 1024 bytes.

In the handheld Hantek DSO1202B/BV, DSO1102B/BV and DSO1062B/BV the display has a 640x480 resolution. This results in a total 307200 bytes of data transmitted for the screenshot.

The PC sends a request without data bytes:

The DSO responds with 30 packets containing 10208 bytes, subcommand 0x01. The 31st packet contains only 960 bytes, and is again followed by a final packet containing a checksum for the screenshot data:

0x21 Read system time
Lets you read the device's system time.

The PC sends a request without data bytes:

The reply contains seven data bytes:

The data bytes:


 * Byte 1: Year (LSB)
 * Byte 2: Year (MSB)
 * Byte 3: Month (1...12)
 * Byte 4: Day (1...31)
 * Byte 5: Hour (0...23)
 * Byte 6: Minute (0...59)
 * Byte 7: Second (0...59)

0x43 Debug messages
The 0x43 messages are not used by the TTScope software, but nevertheless expose interesting functionality. Hantek may be willing to answer some questions about these messages.

0x00 Read FPGA register
Lets you read one of more FPGA registers.

The request for a single register:

The response contains the 4-byte register value:

The request for multiple registers contains a starting register and the number of registers to fetch. The last register in this list (start register + number of registers) must not be higher than 0x4f.

The response contain the register values, 4 bytes per register:

Internally, this calls the firmware function PcUartReadFpgaReg.

Please note: this syntax is temporary, and may be incorrect.

0x01 Read FPGA FIFO contents
Lets you read directly from the FIFO memory. The request contains the buffer length in bytes:

The response contains the FIFO contents:

Please note: this syntax is temporary, and may be incorrect.

0x02 Read DSO firmware variables
The PC sends a request without data bytes:

The reply contains the DSO firmware variable values. These are stored on the DSO in the file and are loaded at boot time. If the file  is not available at boot time, default values are used. These default values are also used when the "Default" button is pressed on the DSO. The stored setups also include these values.

The DSO variables themselves are not yet documented; but at least the following information is stored:
 * current UI (current menu, all user-selectable settings)
 * DSO serial number
 * Firmware version
 * PCB hardware revision

0x03 DSO Selbstkalibrierung auslesen
Die Anfrage ist leer. D.h. sie enthält kein Datenbyte.

Die Antwort beinhaltet die Selbstkalibrierung Informationen, gelesen aus dem DSO Speicher. Die sind auf dem DSO in der Datei /param/sav/chk1kb_yymmdd gespeichert (Aktuell chk1kb_091023, der Zeitstempel kann sich ändern) und werden beim den Bootvorgang geladen. Sollte die Datei "chk1kb" nicht vorhanden sein wird automatisch den Bootvorgang eine leere "Vorlage" im Speicher erstellt.

0x10 Datei lesen
siehe 0x53 Normale Meldungen Datei_lesen

0x11 Virtual remote shell
Allows you to run shell commands. The command sent is stored on the DSO in a temporary file, which is then executed and the output is sent back in the reply packet. Instructions such as "cd / tmp" therefore do not make sense.

Commands that output over 10239 bytes cause the main "dso.exe" process to crash. If you have a shell on the DSO via the UART, you can run "/dso.exe" to restart it. Otherwise, powercycling the unit is necessary.

The request contains only the command:

The reply contains the shell output, followed by LF:

0x40 DSO Firmware Variablen schreiben
Die Anfrage beinhaltet die DSO Firmware Variablen, siehe DSO_Firmware_Variablen_auslesen

Die Antwort ist leer. D.h. sie enthält kein Datenbyte.

Um die Einstellungen zu aktivieren sollte das DSO_Init aufgerufen werden.

0x41 DSO Selbstkalibrierung schreiben
Die Anfrage beinhaltet die Selbstkalibrierung Informationen, siehe DSO_Selbstkalibrierung_auslesen

Die Antwort ist leer. D.h. sie enthält kein Datenbyte.

Um die Einstellungen zu aktivieren sollte das DSO_Init aufgerufen werden.

0x42 FPGA Register beschreiben
Die Anfrage beinhaltet Register Nummer und die Register Daten, siehe auch FPGA_Register_lesen

Die Antwort ist leer. D.h. sie enthält kein Datenbyte.

Intern wird die Firmware Funktion "PcUartWriteFpgaReg" aufgerufen, die mögliche Verwendung muß noch erörtert werden.

'''Bitte beachten - der Syntax ist temporär, evt. auch falsch.'''

0x43 Keycode senden
Ermöglicht einen Keycode zu senden. Der Unterschied zum 0x53 Normales Meldung Tastendruck_auslösen ist dabei sehr einfach, es werden auch speziele Keycodes unterstüzt und nicht nur die die Tasten representieren.

Beispiel1 (DST1xxxB/BV) : Die Taste F6 während sie gedrückt wird hat den debug Keycode <66> (Keycode 0x06 aus der 0x53 Normale MeldungTastendruck_auslösen) + 0x3C). Während die losgelassen wird hat die Taste F6 den debug Keycode (Keycode 0x06 aus der 0x53 Normale MeldungenTastendruck_auslösen) + 0xBB). Vereinfacht gesagt - jeweilige Zeilennummer auf keyprotocol.inf + 0x3B beim Taste drücken und jeweilige Zeilennummer + 0xBA beim loslassen.

Beispiel2 (Hantek DSO5xxxB, Voltcraft DSO-3062C, Tekway DST1xxxB) : Die Taste F6 während sie gedrückt wird hat den debug Keycode <7> (Keycode 0x06 aus der 0x53 Normale MeldungTastendruck_auslösen) + 1). Während die losgelassen wird hat die Taste F6 den debug Keycode (Keycode 0x06 aus der 0x53 Normale MeldungenTastendruck_auslösen) + 1 + 0x80). Vereinfacht gesagt - jeweilige Zeilennummer aus der keyprotocol.inf beim Taste drücken und jeweilige Zeilennummer + 0x80 beim loslassen.

Diese beiden Beispiele zeigen wie unübersichtlich Hantek programmiert.

Die "0x43 Keycode senden" Funktion erlaubt beide debug Keycodes zu senden. Es ist sogar möglich mehrere "clicks" zu senden was sehr interessant für Remote Control sein kann (2 x Utility, 2 x Page, 1 x F1 drucken).

Die Antwort ist leer. D.h. sie enthält kein Datenbyte.

0x44 DSO Buzzer
Aktiviert den Buzzer für die Zeit "BT" (1bit=100ms)

Sobald die Zeit abgelaufen ist schaltet sich der Buzzer selbständig aus.

Die Antwort ist leer. D.h. sie enthält kein Datenbyte.

0x45 Interpolation anpassungen
Erlaubt (temporär) änderungen in der Lagrangeschen Interpolation. Soweit ich verstanden habe kann man die Abgrenzungen (0 bis 1000ps) setzen und die Phasen aller ADCs (eigentlich die Daten aus im FIFOs werden phasenverschoben und nicht die ADCs) ändern (0=0° bis FFFF=360°).

Die Antwort ist leer. D.h. sie enthält kein Datenbyte.

Die Lagrangesche Interpolation ist nur in den TBID < 3 (also Horizontal Ablenkung 2ns/DIV, 4ns/DIV und 8ns/DIV) eingeschaltet. Die mögliche Verwendung muß noch erörtert werden.

'''Bitte beachten - der Syntax ist temporär, evt. auch falsch'''

0x50 Datei senden
Diese Funktion kann benutzt werden um eine beliebige Datei auf das DSO zu übertragen.

Die Anfrage besteht aus drei Paketen wobei das erste Paket (mit Subkommando 0) den vollständigen Dateipfad (Zielpfad), das zweite Paket (mit Subkommando 1) beinhaltet die Daten selber. Sollte die Datei länger als 10000 Bytes sein, werden ein oder mehrere weitere Pakete (mit Subkommando 1) gesendet, solange bis die gesamte Datei gesendet ist. Zum Abschluß wird noch ein Paket gesendet (mit Subkommando 2). Es markiert das Ende der Übertragung und beinhaltet eine Checksumme über alle Bytes der gesendeten Datei.

Nach jedem dieser Pakete sollte einmal die Antwort abgefragt werden. Die Antwort ist leer. D.h. sie enthält kein Datenbyte.

0x60 Datei updaten
Diese Funktion kann benutzt werden um eine beliebige Datei auf dem DSO zu ersetzen.

Die Anfrage besteht aus drei Paketen wobei das erste Paket (mit Subkommando 0) den vollständigen Dateipfad (Zielpfad), das zweite Paket (mit Subkommando 1) beinhaltet die Daten selber. Sollte die Datei länger als 10000 Bytes sein, werden ein oder mehrere weitere Pakete (mit Subkommando 1) gesendet, solange bis die gesamte Datei gesendet ist. Zum Abschluß wird noch ein Paket gesendet (mit Subkommando 2). Es markiert das Ende der Übertragung und beinhaltet eine Checksumme über alle Bytes der gesendeten Datei.

Nach jedem dieser Pakete sollte einmal die Antwort abgefragt werden. Die Antwort ist leer. D.h. sie enthält kein Datenbyte.

Warum auch immer, aber nach dem ersten Paket kommt bei mir eine Antwort mit Fehler = 0x11

was eigentlich für "Datei nicht gefunden" steht. Dennoch wird die angegebene Datei korrekt ersetzt.

0x7F Init DSO
Die Anfrage ist leer. D.h. sie enthält kein Datenbyte.

Dies ruft folgende DSO Subroutinen in der Firmware: PauseSysAcq Acq_InitAcqParam Acq_SyncEqualAcq SyncChDispWhenEnterX SyncBodeAssiant SyncDsoScanSwitch InitCalculationManageParam InitAcqWaveEvent InitDispWaveEvent InitWaveSoftEvent Init_SwapTrig Tdc_SyncTdcTable Limites_Init InitLcdUnwaveareaShow InitLcdWaveAreaShow InitDsoOtherStat UpdateSysRunParam Fpga_SetTrigHoldTime Sync_AutoDispInterval ContinueSysAcq ForceShowWinBar

Die Auswirkung ist nicht die selbe wie bei einem Neustart da nicht alle Init Subroutinen aufgerufen werden, allerdings ausreichend um z.b. DSO Variablen (siehe DSO_Firmware_Variablen_schreiben) oder DSO Selbstkalibrierung Daten (siehe DSO_Selbstkalibrierung_schreiben) zu aktivieren.

Die Antwort ist leer. D.h. sie enthält kein Datenbyte.

.