Ref: www.linotux.ch/arduino/
HC-05 embedded Bluetooth serial communication module has two work modes: order-response work mode and automatic connection work mode . And there are three work roles (Master, Slave and Loopback) at the automatic connection work mode. When the module is at the automatic connection work mode, it will follow the default way set lastly to transmit the data automatically. When the module is at the order-response work mode, user can send the AT command to the module to set the control parameters and sent control order. The work mode of module can be switched by controlling the module PIN (PIO11) input level.
Serial module PINs:
1. PIO8 connects with LED. When the module is power on, LED will flicker. And the flicker style will indicate which work mode is in using since different mode has different flicker time interval.
2. PIO9 connects with LED. It indicates whether the connection is built or not. When the Bluetooth serial is paired, the LED will be turned on. It means the connection is built successfully.
3. PIO11 is the work mode switch. When this PIN port is input high level, the work mode will become order-response work mode. While this PIN port is input low level or suspended in air, the work mode will become automatic connection work mode. 4. The module can be reset if it is re-powered since there is a reset circuit at the module.
1. How to get to the AT mode?
Method 1:
Step 1: Input low level to PIN34.
Step 2: Supply power to the module.
Step 3: Input high level to the PIN34.
Then the module will enter to AT mode. The baud rate is as same as the communication time, such as 9600 etc.
Method 2:
Step 1: Connect PIN34 to the power supply PIN.
Step 2: Supply power to module (the PIN34 is also supplied with high level since the PIN34 is connected with power supply PIN). Then the module will enter to AT module. But at this time, the baud rate is 38400. In this way, user should change the baud rate at the AT mode, if they forget the communication baud rate.
2. How to get to the communication mode?
Step 1: Input low level to PIN34.
Step 2: Supply power to the module. Then the module will enter to communication mode. It can be used for pairing.
3. How to set this module be the master role ?
Step 1: Input high level to PIO11.
Step 2: Supply power to the module. And the module will enter to the order-response work mode.
Step 3: Set the parameters of the super terminal or the other serial tools (baud rate: 38400, data bit:8, stop bit:1, no parity bit, no Flow Control)
Step 4: Sent the characters “AT+ROLE=1\r\n” through serial, then receive the characters “OK\r\n”. Here, “\r\n” is the CRLF.
Step 5: Input low level to PIO, and supply power to the module again. Then this module will become master role and search the other module (slave role) automatically to build the connection.
Notes.
1. HC-03 and HC-05’s command should end up with “\r\n”. It means when you finish programming, you should add terminator (“ENTER” or “0x0d 0x0a”) to the program. It’s different from HC-04 and HC-06 (They don’t need terminator).
2. The most common commands for HC-03 and HC-05 are: AT+ROLE (set master –slave), AT+CMODE( set address pairing) , AT+PSWD (set password). If you want the master module has the function of remembering slave module, the most simply way is: First, set AT+CMODE=1. Make the master module pair with the slave module. Second, set AT+CMODE=0. Then the master module just can make pair with that specified slave module.
3. When PIN34 keeps high level, all commands can be used. Otherwise, only some of them can be used.
Bluetooth Module AT Commands
(AT command is case- sensitive, should end up with terminator (“enter” or “\r\n”).)
1. Test
| Command | Response | Parameter |
| AT | OK | None |
2. Reset
| Command | Response | Parameter |
| AT+RESET | OK | None |
3. Get the soft version
| Command | Response | Parameter |
| AT+VERSION? | +VERSION: <Param> OK | Param: Version number |
Example :
at+version?\r\n
+VERSION:2.0-20100601
OK
4. Restore default status
| Command | Response | Parameter |
| AT+ORGL | OK | None |
The parameter of default status:
- Device type: 0
- Inquire code: 0x009e8b33
- Module work mode: Slave Mode
- Connection mode: Connect to the Bluetooth device specified
- Serial parameter: Baud rate: 38400 bits/s; Stop bit: 1 bit; Parity bit: None.
- Passkey: “1234”
- Device name: “H-C-2010-06-01”
5. Get module Bluetooth address
| Command | Response | Parameter |
| AT+ADDR? | +ADDR: <Param> OK | Param: Bluetooth address |
Bluetooth address will show as this way: NAP: UAP: LAP(Hexadecimal)
Example:
Module Bluetooth address: 12: 34: 56: ab: cd: ef
at+addr?\r\n
+ADDR:1234:56:abcdef
OK
6. Set/ inquire device’s name
| Command | Response | Parameter |
| AT+NAME=<Param> | OK | |
| AT+NAME? | 1. +NAME:<Param>
OK—-success 2. FAIL—-failure |
Param: Bluetooth device name Default: “HC-05” |
Example:
AT+NAME=HC-05\r\n //set the module device name: “HC-05”
OK
AT+NAME= “HC-05”\r\n //set the module device name: “HC-05”
OK
at+name=Beijin\r\n //set the module device name: “Beijin”
OK
at+name= “Beijin”\r\n //set module device name : “Beijin”
OK
at+name?\r\n
+NAME: Bei jin
OK
7. Get the remote Bluetooth device’s name
| Command | Response | Parameter |
| AT+RNAME?<Param1> | 1. +NAME:<Param1> OK—-success
2. FAIL—-failure |
Param1: Remote Bluetooth device address
Param2: Remote Bluetooth device address |
Bluetooth address will show as this way: NAP:UAP:LAP (Hexadecimal)
Example:
Bluetooth device address: 00:02:72: od: 22 : 24; device name: Bluetooth
at+rname? 0002,72,od2224\r\n
+RNAME:Bluetooth
OK
8. Set/ inquire module role
| Command | Response | Parameter |
| AT+ROLE=<Param> | OK | Param: 0—- Slave role 1—- Master role 2—- Slave-Loop role Default: 0 |
| AT+ROLE? | +ROLE:<Param> OK |
Role introduction:
- Slave (slave role)—-Passive connection;
- Slave-Loop—-Passive connection, receive the remote Bluetooth master device data and send it back to the master device;
- Master (master role)—-Inquire the near SPP Bluetooth slave device, build connection with it positively, and build up the transparent data transmission between master and slave device.
9. Set/inquire device type
| Command | Response | Parameter |
| AT+CLASS=<Param> | OK | Param: device type Bluetooth device type is a 32-bit parameter indicates the device type and what type can be supported. Default: 0 More information is provided at the appendix 1(device type introduction). 0—- Slave role 1—- Master role 2—- Slave-Loop role Default: 0 |
| AT+CLASS? | 1. + CLASS:<Param> OK—-success 2. FAIL—-failure |
For inquiring the custom Bluetooth device from around Bluetooth devices quickly and effectively, user can set the module to be non-standard Bluetooth device type, such as 0x1f1f (Hexadecimal).
10. Set/ inquire-Inquire access code
| Command | Response | Parameter |
| AT+IAC=<Param> | 1. OK—-success 2. FAIL—-failure |
Param: Inquire access code Default: 9e8b33 The more information is provided at the appendix 2(Inquire access code introduction). |
| AT+IAC? | +IAC: <Param> OK |
Access code is set to be GIAC type (General Inquire Access Code:0x9e8b33), and used for seeking ( or being sought by ) all the Bluetooth devices around. For inquiring (or being inquiring by) the custom Bluetooth device from around Bluetooth devices quickly and effectively, user can set the inquire access code to be the other type number (not GIAC nor LIAC), such as 9e8b3f.
Example:
AT+IAC=9e8b3f\r\n OK AT+IAC?\r\n
+IAC: 9e8b3f
OK
11. Set/ inquire – Inquire access mode
| Command | Response | Parameter |
| AT+INQM=<Param>, <Param2>,<Param3> |
1. OK—-success 2. FAIL—-failure |
Param: Inquire access mode 0—-inquiry_mode_standard 1—-inquiry_mode_rssi Param2: the maximum of Bluetooth devices response Param3:The maximum of limited inquiring time The range of limited time: 1~48 ( Corresponding time:1.28s~61.44s) Default: 1, 1, 48 |
| AT+ INQM? | +INQM:<Param>,<Param2>,<P aram3> OK |
Example:
AT+INQM=1,9,48\r\n //Set Inquire access mode: 1) has RSSI signal intensity indicator, 2) stop inquiring once more than 9 devices response, 3) limited time is 48*l. 28=61.44s.
OK
AT+INQM\r\n
+INQM:1, 9, 48
OK
12. Set/Inquire- passkey
| Command | Response | Parameter |
| AT+PSWD=<Param> | OK | Param: passkey Default: “1234” |
| AT+PSWD? | +PSWD : OK |
13.Set/ Inquire- serial parameter
| Command | Response | Parameter |
| AT+UART=<Param>,< Param2>,<Param3> |
OK | Param1: baud rate( bits/s) The value (Decimal) should be one of the following: 4800 9600 19200 38400 57600 115200 23400 460800 921600 1382400 Param2:stop bit: 0—-1 bit 1—-2 bits Param3: parity bit 0—-None 1—-Odd parity 2—-Even parity Default: 9600, 0, 0 |
| AT+UART? | +UART=<Param>,<Para m2>,<Param3> OK |
Example:
Set baud rate to be 115200, stop bit to be 2 bits, parity bit to be even parity. AT+UART=115200,1,2,\r\n
OK
AT+UART?
+UART:115200,1,2
OK
14. Set/ Inquire – connection mode
| Command | Response | Parameter |
| AT+CMODE=<Param> | OK | Param: 0—-connect the module to the specified Bluetooth address. (Bluetooth address can be specified by the binding command) 1—-connect the module to any address (The specifying address has no effect for this mode.) 2—-Slave-Loop Default connection mode: 0 |
| AT+ CMODE? | +CMODE:<Param> OK |
15. Set/Inquire – bind Bluetooth address
Bluetooth address will show as this way: NAP: UAP:LAP(Hexadecimal)
| Command | Response | Parameter |
| AT+BIND=<Param> | OK | Param—-Bluetooth address needed to be bind Default address: 00:00:00:00:00:00 |
| AT+BIND? | +BIND:<Param> OK |
This command is effective only when the module wants to connect to the specified Bluetooth address. Example: The module is at connection mode which connects to specified Bluetooth address, and the specified address is 12:34:56:ab:cd:ef. Command and the response show as follow:
AT+BIND=1234, 56, abcdef\r\n
OK
AT+BIND?\r\n
+BIND:1234:56:abcdef
OK
16. Set/Inquire – drive indication of LED and connection status
| Command | Response | Parameter |
| AT+POLAR=<Param1>, <Param1> |
OK | Param1:The value is 0—-PI08 outputs low level and turn on LED 1—-PI08 outputs high level and turn on LED Param2:The value is 0—-PI09 output low level, indicate successful connection 1—-PI09 output high level, and indicate successful connection Default: 1, 1 |
| AT+POLAR? | +POLAR=<Param1>, <Param1> OK |
HC-05 Bluetooth module definition: The output of PI08 drives indication of LED work mode; the output of PI09 indicates the connection status.
Example:
PI08 outputs low level and turn on LED, PI09 outputs high level and indicates successful connection. Command and response show as follow:
AT+POLAR=0, 1\r\n
OK
AT+POLAR?\r\n
+POLAR=0, 1
OK
17. Set PIO single port output
| Command | Response | Parameter |
| AT+PIO=<Param1>,<Param2> | OK | Param1: PIO port number(Decimal) Param2: PIO port status
0—-low level 1—-high level |
HC-05 Bluetooth module provides the user with the ports (PI00~PI07 and PI010) which can extern another input and output ports.
Example:
1. PI010 port outputs high level
AT+PI0=10, 1\r\n
OK
2. PI010 port outpust low level
AT+PI0=10, 0\r\n
OK
18. Set PIO multiple port output
| Command | Response | Parameter |
| AT+MPIO=<Param> | OK | Param: Mask combination of PIO ports number (Decimal) |
HC-05 Bluetooth module provides the ports (PI00~PI07 and PI010) which can extern another input and output ports to the user.
1. Mask of PIO port number = (1<<port number)
2. Mask combination of PIO ports number= (PIO port number mask 1 | PIO port number mask 2 | ….)
Example :
PI02 port number mask=(1<<2) =0x004
PI010 port number mask =(1<<10)=0x400
Mask combination of PI02 and PI010 port number=(0x004|0x400)=0x404
Example:
1. PI010 and PI02 ports output high level
AT+MPI0=404\r\n
OK
2. PI04 port output high level
AT+PI0=004\r\n
OK
3. PI010 port output high level
AT+PI0=400\r\n
OK
4. All ports output low level
AT+MPI0=0\r\n
OK
19. Inquire PIO port input
| Command | Response | Parameter |
| AT+MPIO? | +MPIO: <Param> OK |
Param—-PIO port value (16bits) Param[0]=PI00 Param[1]=PI01 Param[2]=PI02 …… Param[10]=PI010 Param[11]=PI011 |
HC-05 Bluetooth module provides the user with the ports (PI00~PI07 and PI010) which can extern another input and output ports.
20. Set/ Inquire page scan and inquire scan parameter
| Command | Response | Parameter |
| AT+IPSCAN=<Param1>, <Param2>, <Param3>,<Param4>AT+I PSCAN? |
OK +IPSCAN: <Param1>,<Param2>, <Param3>,<Param4> OK |
Param1:time interval of inquiring Param2: duration in inquiring Param3: time interval of paging Param4: duration in paging The above parameters are decimal. Default:1024,512,1024,512 |
Example:
at+ipscan=1234,500,1200,250\r\n
OK
at+ipscan?
+IPSCAN:1234,500,1200,250
21. Set/ Inquire—SHIFF energy parameter
| Command | Response | Parameter |
| AT+SNIFF=<Param1> ,<Param2>, <Param3>,<Param4> |
OK | Param1: maximum time Param2: minimum time Param3: test time Param4: limited time The above parameters are decimal. Default : 0,0,0,0 |
| AT+IPSCAN? | +SNIFF: <Param1>,<Param2>,<Par am3>,<Param4> |
22. Set/ Inquire safe and encryption mode
| Command | Response | Parameter |
| AT+SENM=<Param >,<Param2>, |
1. OK—-success 2. FAIL—-failure | Param: the value of safe mode: 0—-sec_mode0+off 1—-sec_mode1+non_secure 2—-sec_mode2_service 3—-sec_mode3_link 4—-sec_mode_unknown Param2: the value of encryption mode: 0—-hci_enc_mode_off 1—-hci_enc_mode_pt_to_pt 2—-hci_enc_mode_pt_to_pt_and_bcast Default: 0,0 |
| AT+ SENM? | +SENM:<Param>,<Param 2>, OK |
23. Delete authenticated device in the Bluetooth pair list
| Command | Response | Parameter |
| AT+PMSAD=<Param> | OK | Param: Bluetooth device address |
Example:
Delete the device ( address: 12:34:56:ab:cd:ef ) in the blue pair list at+rmsad=1234,56,abcdef\r\n
OK //successful deletion Or
at+rmsad=1234,56,abcdef\r\n
FAIL //There is no the Bluetooth device whose address is 12:34:56:ab:cd:ef in the pair list.
24. Delete all authenticated devices in the pair list
| Command | Response | Parameter |
| AT+RMAAD | OK | None |
Example: Move all devices away from the pair list.
at+rmaad\r\n
OK
25. Seek the authenticated device in the Bluetooth pair list
| Command | Response | Parameter |
| AT+FSAD=<Param> | 1. OK—-success 2. FAIL—-failure |
Param: Bluetooth device address |
Example: Seek the authenticated device (address: 12:34:56:ab:cd:ef) in the pair list at+fsad=1234,56,abcdef\r\n
OK //the Bluetooth device whose address is 12:34:56:ab:cd:ef is found.
at+fsad=1234,56,abcde0\r\n
FAIL //There is no the Bluetooth device whose address is 12:34:56:ab:cd:e0 in the pair list.
26. Get the authenticated device count from the pair list
| Command | Response | Parameter |
| AT+ADCN? | +ADCN:<Param> OK |
Param: Authenticated Device Count |
Example:
at+adcn?
+ADCN:0 //There is no authenticated device in the pair list.
OK
27. Get the Bluetooth address of Most Recently Used Authenticated Device
| Command | Response | Parameter |
| AT+MRAD? | +MRAD : <Param> OK |
Param: the Bluetooth address of Most Recently Used Authenticated Device |
Example:
at+mrad?
+MRAD:0:0:0 //There is no device that has been used recently.
OK
28. Get the work status of Bluetooth module
| Command | Response | Parameter |
| AT+STATE? | +STATE: <Param> OK |
Param: work status of module Return value： “INITIALIZED” —-initialized status “READY” —- ready status “PAIRABLE” —-pairable status “PAIRED” —-paired status “INQUIRING” —-inquiring status “CONNECTING”—-connecting status “CONNECTED”—-connected status “DISCONNECTED”—-disconnected status “NUKNOW”—-unknown status |
Example:
at+state?
+STATE:INITIALIZED //initialized status
OK
29. Initialize the SPP profile lib
| Command | Response | Parameter |
| AT+INIT | 1. OK—-success 2. FAIL—-failure |
None |
30. Inquire Bluetooth device
| Command | Response | Parameter |
| AT+INQ | +INQ: <Param1>,<Param2>,<Param3>, …… OK |
Param1: Bluetooth address Param2: device type Param3: RSSI signal intensity |
Example 1:
at+init\r\n //Initialize the SPP profile lib( can’t repeat initialization)
OK
at+iac=9e8b33\r\n //Inquire Bluetooth device has an access code
OK
at+class=0\r\n //Inquire the Bluetooth device type
at+inqm=1,9,48\r\n //Inquire mode: 1) has the RSSI signal intensity indication, 2) stop inquiring if more than 9 Bluetooth devices response, 3) limited time in inquiring is 48*1.28=61.44s.
at+inq\r\n //inquire the Bluetooth device around
+INQ:2:72:D2224,3E0104,FFBC
+INQ:1234:56:0,1F1F,FFC1
+INQ:1234:56:0,1F1F,FFC0
+INQ:1234:56:0,1F1F,FFC1
+INQ:2:72:D2224,3F0104,FFAD
+INQ:1234:56:0,1F1F,FFBE
+INQ:1234:56:0,1F1F,FFC2
+INQ:1234:56:0,1F1F,FFBE
+INQ:2:72:D2224,3F0104,FFBC
OK
Example 2:
at+iac=9e8b33\r\n //inquire the Bluetooth device has an access code
OK
at+class=1f1f\r\n //inquire the Bluetooth device whose device type is 0x1f1f
OK
at+inqm=1,9,48\r\n //inquire mode: 1) has the RSSI signal intensity indication, 2) stop inquiring if more than 9 Bluetooth devices response, 3) limited time in inquiring is 48*1.28=61.44s
at+inq\r\n //filter and inquire the Bluetooth device around
+INQ:1234:56:0,1F1F,FFC2
+INQ:1234:56:0,1F1F,FFC1
+INQ:1234:56:0,1F1F,FFC1
+INQ:1234:56:0,1F1F,FFC1
+INQ:1234:56:0,1F1F,FFC2
+INQ:1234:56:0,1F1F,FFC1
+INQ:1234:56:0,1F1F,FFC1
+INQ:1234:56:0,1F1F,FFC0
+INQ:1234:56:0,1F1F,FFC2
OK
Example 3:
at+iac=9e8b3f\r\n //inquire the Bluetooth device whose access code is 0x9e8b3f
OK
at+class=1f1f\r\n //inquire the Bluetooth device whose device type is 0x1f1f
OK
at+inqm=1,1,20\r\n //inquire mode: 1) Has the RSSI signal intensity indication, 2) stop inquiring if more than 1 Bluetooth device response, 3) limited time in inquiring is 20*1.28=25.6s
at+inq\r\n //filter and inquire the Bluetooth device around
+INQ:1234:56:ABCDEF,1F1F,FFC2
OK
31. Cancel Bluetooth device
| Command | Response | Parameter |
| AT+INQC | OK | None |
32. Set pair
| Command | Response | Parameter |
| AT+PAIR=<Param1>,<Param2> | 1. OK—-success 2. FAIL—-failure |
Param1: Bluetooth address of remote device Param2: limited time of connection (second) |
Example: Make pair with the remote Bluetooth device( address:12:34:56:ab:cd:ef), the limited time is 20s.
at+pai=1234,56,abcdef,20\r\n
OK
33. Connect device
| Command | Response | Parameter |
| AT+LINK=<Param> | 1. OK—-success 2. FAIL—-failure |
Param: Bluetooth address of remote device |
Example: Connect with the remote Bluetooth device (address: 12:34:56:ab:cd:ef)
at+fsad=1234,56,abcdef\r\n //To check whether the Bluetooth device (address: 12:34:56:ab:cd:ef) is in the pair list or not.
OK
at+link=1234,56,abcdef\r\n //The Bluetooth device (address: 12:34:56:ab:cd:ef) is in the pair list. The connection can be built directly without inquiring.
OK
34. Disconnection
| Command | Response | Parameter |
| AT+DISC | 1.+DISC:SUCCESS—-successful Disconnection OK 2.+DISC:LINK_LOSS—-lose the connection OK 3.+DISC:NO_SLC—-No SLC connection OK 4、+DISC:TIMEOUT—-disconnection timeout OK 5、+DISC:ERROR—-disconnection error OK |
None |
35. Enter to energy mode
| Command | Response | Parameter |
| AT+ENSNIFF=<Param> | OK | Param: Bluetooth address of device |
36. Exit energy mode
| Command | Response | Parameter |
| AT+EXSNIFF=<Param> | OK | Param: Bluetooth address of device |
Appendix 1：Introduction of AT command error code
The form of error —- ERROR:(error_code)
| error_code(Hexadecimal) | Note |
| 0 | AT command error |
| 1 | Default result |
| 2 | PSKEY write error |
| 3 | Too long length of device name (more than 32 bytes). |
| 4 | No device name |
| 5 | Bluetooth address: NAP is too long. |
| 6 | Bluetooth address: UAP is too long. |
| 7 | Bluetooth address: LAP is too long. |
| 8 | No PIO number’s mask |
| 9 | No PIO number |
| A | No Bluetooth devices. |
| B | Too length of devices |
| C | No inquire access code |
| D | Too long length of inquire access code |
| E | Invalid inquire access code |
| F | The length of passkey is 0. |
| 10 | Too long length of passkey (more than 16 bytes) |
| 11 | Invalid module role |
| 12 | Invalid baud rate |
| 13 | Invalid stop bit |
| 14 | Invalid parity bit |
| 15 | Authentication device is not at the pair list. |
| 16 | SPP lib hasn’t been initialized. |
| 17 | SPP lib has been repeated initialization. |
| 18 | Invalid inquire mode |
| 19 | Too long inquire time |
| 1A | No Bluetooth address |
| 1B | Invalid safe mode |
| 1C | Invalid encryption mode |
Appendix 2: The introduction of devices
The Class of Device/Service(CoD) is a 32 bits number that of 3 field specifies the service supported by the device. Another field specifies the minor device class, which describes the device type in more detail.
The Class of Device /Service (CoD) field has a variable format. The format is indicated using the ’within the CoD .The length of the Format Type field is variable and ends with two bits different from’11’.The version field starts at the least significant bit of the CoD and may extend upwards. In the ’format#1’ of the CoD (format Type field =00), 11 bits are assigned as a bit –mask (multiple bits can be set) each bit corresponding to a high level generic category of service class. Currently 7 categories are defined. These are primarily of a’ public service’ nature. The remaining 11 bits are used for indicating device type category and other device-specific characteristics. Any reserved but otherwise unassigned bits, such as in the Major Service Class field, should be to 0.
1. MAJOR SERVICE CLASSES
Bit no Major Service Class
- 13 Limited Discoverable Mode
- 14 (reserved)
- 15 (reserved)
- 16 Positioning(Location identification)
- 17 Networking (LAN, Ad hoc, … )
- 18 Rendering (Printing ,Speaker,…)
- 19 Capturing (Scanner, Microphone,…)
- 20 0bject Transfer (v-Inbox, v-Folder,…)
- 21 Audio (Speaker, Microphone, Headset service,…)
- 22 Telephony (Cordless telephony, Modem, Headset service,…)
- 23 Information (WEB-server, WAP- server,…)
2. MAJOR DEVICE CLASSES
The Major Class segment is the highest level of granularity for defining a Bluetooth Device. The main function of a device is used for determining the major Class grouping. There are 32 different possible major classes.
- 0 0 0 0 0 Miscel laneous
- 0 0 0 0 1 Computer (desktop, notebook, PDA, organizers,…)
- 0 0 0 1 0 Phone (cellular ,cordless ,payphone, modem,…)
- 0 0 0 1 1 LAN/Network Access point 0 0 1 0 0 Audio/Video (headset, speaker, stereo, video display, vcr …)
- 0 0 1 0 1 Periphereal (mouse, joystick, keyboards.…)
- 0 0 1 1 0 Imaging (printing, scanner, camera, display,…)
- 1 1 1 1 1 Uncategorized, specific device code not specified
- X X X X All other values reserved