STMicroelectronics STM32L0 series, STM32L1 series, STM32F0 series, STM32F1 series, STM32F2 series, STM32F3 series, STM32F4 series microcontroller Application note

AN3155
Application note
USART protocol used in the STM32 bootloader
Introduction
This application note describes the USART protocol used in the STM32 microcontroller
bootloader. It details each supported command. For more information about the USART
hardware resources and requirements for your device bootloader, please refer to the
“STM32 system memory boot mode” application note (AN2606).
Refer to Table 1 for the list of applicable microcontrollers.
Related documents
They are available from www.st.com:
•
Application note “STM32 system memory boot mode” (AN2606)
Table 1. Applicable products
Type
Part number or product series
STM32L0 series
STM32L1 series
STM32F0 series
Microcontrollers STM32F1 series
STM32F2 series
STM32F3 series
STM32F4 series
June 2014
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www.st.com
Contents
AN3155
Contents
1
USART bootloader code sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2
Choosing the USARTx baud rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3
2.1
Minimum baud rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.2
Maximum baud rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Bootloader command set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1
Get command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.2
Get Version & Read Protection Status command . . . . . . . . . . . . . . . . . . . 10
3.3
Get ID command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
3.4
Read Memory command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.5
Go command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.6
Write Memory command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.7
Erase Memory command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.8
Extended Erase Memory command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.9
Write Protect command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3.10
Write Unprotect command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
3.11
Readout Protect command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
3.12
Readout Unprotect command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
4
Bootloader protocol version evolution . . . . . . . . . . . . . . . . . . . . . . . . . 35
5
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
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AN3155
List of tables
List of tables
Table 1.
Table 2.
Table 3.
Table 4.
Applicable products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
USART bootloader commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Bootloader protocol versions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
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List of figures
AN3155
List of figures
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
Figure 13.
Figure 14.
Figure 15.
Figure 16.
Figure 17.
Figure 18.
Figure 19.
Figure 20.
Figure 21.
Figure 22.
Figure 23.
Figure 24.
Figure 25.
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Bootloader for STM32 with USART . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Get command: host side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Get command: device side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Get Version & Read Protection Status command: host side . . . . . . . . . . . . . . . . . . . . . . . 10
Get Version & Read Protection Status command: device side. . . . . . . . . . . . . . . . . . . . . . 11
Get ID command: host side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Get ID command: device side. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Read Memory command: host side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Read Memory command: device side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Go command: host side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Go command: device side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Write Memory command: host side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Write Memory command: device side. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Erase Memory command: host side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Erase Memory command: device side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Extended Erase Memory command: host side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Extended Erase Memory command: device side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Write Protect command: host side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Write Protect command: device side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Write Unprotect command: host side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Write Unprotect command: device side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Readout Protect command: host side. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Readout Protect command: device side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Readout Unprotect command: host side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Readout Unprotect command: device side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
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1
USART bootloader code sequence
USART bootloader code sequence
Figure 1. Bootloader for STM32 with USART
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Once the system memory boot mode is entered and the STM32 microcontroller has been
configured (for more details refer to application note AN2606 “STM32 system memory boot
mode”) the bootloader code begins to scan the USARTx_RX line pin, waiting to receive the
0x7F data frame: one start bit, 0x7F data bits, even parity bit and one stop bit.
The duration of this data frame is measured using the Systick timer. The count value of the
timer is then used to calculate the corresponding baud rate factor with respect to the current
system clock.
Next, the code initializes the serial interface accordingly. Using this calculated baud rate, an
acknowledge byte (0x79) is returned to the host, which signals that the STM32 is ready to
receive commands.
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Choosing the USARTx baud rate
2
AN3155
Choosing the USARTx baud rate
The calculation of the serial baud rate for USARTx, from the length of the first byte that is
received, is used to operate the bootloader within a wide range of baud rates. However, the
upper and lower limits have to be kept, in order to ensure proper data transfer.
For a correct data transfer from the host to the microcontroller, the maximum deviation
between the internal initialized baud rate for USARTx and the real baud rate of the host
should be below 2.5%. The deviation (fB, in percent) between the host baud rate and the
microcontroller baud rate can be calculated using the formula below:
baud rate – Host baud rate
f B = STM32
------------------------------------------------------------------------------------------- × 100%
STM32 baud rate
, where fB ≤ 2.5%.
This baud rate deviation is a nonlinear function depending on the CPU clock and the baud
rate of the host. The maximum of the function (fB) increases with the host baud rate. This is
due to the smaller baud rate prescale factors, and the implied higher quantization error.
2.1
Minimum baud rate
The lowest tested baud rate (BLow) is 1200. Baud rates below BLow would cause the
SysTick timer to overflow. In this event, USARTx would not be correctly initialized.
2.2
Maximum baud rate
BHigh is the highest baud rate for which the deviation still does not exceed the limit. All baud
rates between BLow and BHigh are below the deviation limit.
The highest tested baud rate (BHigh) is 115 200.
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3
Bootloader command set
Bootloader command set
The supported commands are listed in Table 2 below. Each command is further described in
this section.
Table 2. USART bootloader commands
Command(1)
Command code
Command description
Get(2)
0x00
Gets the version and the allowed commands supported
by the current version of the bootloader
Get Version & Read
Protection Status(2)
0x01
Gets the bootloader version and the Read Protection
status of the Flash memory
Get ID(2)
0x02
Gets the chip ID
Read Memory(3)
0x11
Reads up to 256 bytes of memory starting from an
address specified by the application
Go(3)
0x21
Jumps to user application code located in the internal
Flash memory or in SRAM
Write Memory(3)
0x31
Writes up to 256 bytes to the RAM or Flash memory
starting from an address specified by the application
Erase(3)(4)
0x43
Erases from one to all the Flash memory pages
Extended Erase(3)(4)
0x44
Erases from one to all the Flash memory pages using
two byte addressing mode (available only for v3.0 usart
bootloader versions and above).
Write Protect
0x63
Enables the write protection for some sectors
Write Unprotect
0x73
Disables the write protection for all Flash memory sectors
Readout Protect
0x82
Enables the read protection
0x92
Disables the read protection
Readout
Unprotect(2)
1. If a denied command is received or an error occurs during the command execution, the bootloader sends
NACK byte and goes back to command checking.
2. Read protection – When the RDP (read protection) option is active, only this limited subset of commands is
available. All other commands are NACKed and have no effect on the device. Once the RDP has been
removed, the other commands become active.
3. Refer to STM32 product datasheets and to the “STM32 microcontroller system memory boot mode”
application note (AN2606) to know which memory areas are valid for these commands.
4. Erase (x043) and Extended Erase (0x44) are exclusive. A device may support either the Erase command
or the Extended Erase command but not both.
Communication safety
All communications from the programming tool (PC) to the device are verified by:
1.
checksum: received blocks of data bytes are XORed. A byte containing the computed
XOR of all previous bytes is added to the end of each communication (checksum byte).
By XORing all received bytes, data + checksum, the result at the end of the packet
must be 0x00
2.
for each command the host sends a byte and its complement (XOR = 0x00)
3.
UART: parity check active (even parity)
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Bootloader command set
AN3155
Each packet is either accepted (ACK answer) or discarded (NACK answer):
3.1
•
ACK = 0x79
•
NACK = 0x1F
Get command
The Get command allows you to get the version of the bootloader and the supported
commands. When the bootloader receives the Get command, it transmits the bootloader
version and the supported command codes to the host, as described in Figure 2.
Figure 2. Get command: host side
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Bootloader command set
Figure 3. Get command: device side
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The STM32 sends the bytes as follows:
Byte 1:
ACK
Byte 2:
N = 11 = the number of bytes to follow – 1 except current and ACKs.
Byte 3:
Bootloader version (0 < Version < 255), example: 0x10 = Version 1.0
Byte 4:
0x00
– Get command
Byte 5:
0x01
– Get Version and Read Protection Status
Byte 6:
0x02
– Get ID
Byte 7:
0x11
– Read Memory command
Byte 8:
0x21
– Go command
Byte 9:
0x31
– Write Memory command
Byte 10:
0x43 or
0x44
– Erase command or Extended Erase command (these commands are
exlusive)
Byte 11:
0x63
– Write Protect command
Byte 12:
0x73
– Write Unprotect command
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Bootloader command set
AN3155
Byte 13:
0x82
– Readout Protect command
Byte 14:
0x92
– Readout Unprotect command
Last byte (15): ACK
3.2
Get Version & Read Protection Status command
The Get Version & Read Protection Status command is used to get the bootloader version
and the read protection status. When the bootloader receives the command, it transmits the
information described below (version, read protection: number of times it was enabled and
disabled) to the host.
Figure 4. Get Version & Read Protection Status command: host side
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1. GV = Get Version & Read Protection Status.
10/37
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AN3155
Bootloader command set
Figure 5. Get Version & Read Protection Status command: device side
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1. GV = Get Version & Read Protection Status.
The STM32 sends the bytes as follows:
3.3
Byte 1:
ACK
Byte 2:
Bootloader version (0 < Version ≤ 255), example: 0x10 = Version 1.0
Byte 3:
Option byte 1: 0x00 to keep the compatibility with generic bootloader protocol
Byte 4:
Option byte 2: 0x00 to keep the compatibility with generic bootloader protocol
Byte 5:
ACK
Get ID command
The Get ID command is used to get the version of the chip ID (identification). When the
bootloader receives the command, it transmits the product ID to the host.
The STM32 device sends the bytes as follows:
Byte 1:
ACK
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Bootloader command set
Byte 2:
AN3155
N = the number of bytes – 1 (N = 1 for STM32), except for current byte and
ACKs.
Bytes 3-4: PID(1) byte 3 = 0x04, byte 4 = 0xXX
Byte 5:
ACK
1. PID stands for product ID. Byte 1 is the MSB and byte 2, the LSB of the ID.
Figure 6. Get ID command: host side
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1. GID = Get ID.
12/37
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AN3155
Bootloader command set
Figure 7. Get ID command: device side
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1. GID = Get ID.
3.4
Read Memory command
The Read Memory command is used to read data from any valid memory address (see
note) in RAM, Flash memory and the information block (System memory or option byte
areas).
Note:
Refer to STM32 product datasheets and to the “STM32 microcontroller system memory
boot mode” application note (AN2606) for more details about the valid memory addresses
for the device you are using.
When the bootloader receives the Read Memory command, it transmits the ACK byte to the
application. After the transmission of the ACK byte, the bootloader waits for an address (4
bytes, byte 1 is the address MSB and byte 4 is the LSB) and a checksum byte, then it
checks the received address. If the address is valid and the checksum is correct, the
bootloader transmits an ACK byte, otherwise it transmits a NACK byte and aborts the
command.
When the address is valid and the checksum is correct, the bootloader waits for the number
of bytes to be transmitted – 1 (N bytes) and for its complemented byte (checksum). If the
checksum is correct it then transmits the needed data ((N + 1) bytes) to the application,
starting from the received address. If the checksum is not correct, it sends a NACK before
aborting the command.
The host sends bytes to the STM32 as follows:
Bytes 1-2:
0x11+0xEE
Wait for ACK
Bytes 3 to 6: start address
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Bootloader command set
Byte 7:
AN3155
•
byte 3: MSB
•
byte 6: LSB
Checksum: XOR (byte 3, byte 4, byte 5, byte 6)
Wait for ACK
Byte 8:
The number of bytes to be read – 1 (0 < N ≤ 255);
Byte 9:
Checksum: XOR byte 8 (complement of byte 8)
Figure 8. Read Memory command: host side
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Note:
14/37
Some products may return two NACKs instead of one single NACK when Read Protection
(RDP) is active (or Read Potection level 1 is active). To know if a given product returns one
DocID17066 Rev 6
AN3155
Bootloader command set
single NACK or two NACKs in this situation, please refer to the known limitations section
relative to that product in AN2606.
Figure 9. Read Memory command: device side
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Bootloader command set
3.5
AN3155
Go command
The Go command is used to execute the downloaded code or any other code by branching
to an address specified by the application. When the bootloader receives the Go command,
it transmits the ACK byte to the application. After the transmission of the ACK byte, the
bootloader waits for an address (4 bytes, byte 1 is the address MSB and byte 4 is LSB) and
a checksum byte, then it checks the received address. If the address is valid and the
checksum is correct, the bootloader transmits an ACK byte, otherwise it transmits a NACK
byte and aborts the command.
When the address is valid and the checksum is correct, the bootloader firmware performs
the following:
•
it initializes the registers of the peripherals used by the bootloader to their default reset
values
•
it initializes the user application’s main stack pointer
•
it jumps to the memory location programmed in the received ‘address + 4’ (which
corresponds to the address of the application’s reset handler).
For example if the received address is 0x0800 0000, the bootloader will jump to the
memory location programmed at address 0x0800 0004.
In general, the host should send the base address where the application to jump to is
programmed
Figure 10. Go command: host side
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16/37
Valid addresses for the Go command are in RAM or Flash memory (refer to STM32 product
datasheets and to the “STM32 microcontroller system memory boot mode” application note
- AN2606 for more details about the valid memory addresses for the device you are using).
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AN3155
Bootloader command set
All other addresses are considered not valid and are NACKed by the device.
When an application is loaded into RAM and then a jump is made to it, the program must be
configured to run with an offset to avoid overlapping with the first RAM memory used by the
bootloader firmware (refer to STM32 product datasheets and to the “STM32 microcontroller
system memory boot mode” application note - AN2606 for more details about the RAM
offset for the device you are using).
The Jump to the application works only if the user application sets the vector table correctly
to point to the application address.
Some products may return two NACKs instead of one single NACK when Read Protection
(RDP) is active (or Read Potection level 1 is active). To know if a given product returns one
single NACK or two NACKs in this situation, please refer to the known limitations section
relative to that product in AN2606.
Figure 11. Go command: device side
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Bootloader command set
AN3155
The host sends bytes as follow to the STM32:
Byte 1:
0x21
Byte 2:
0xDE
Wait for ACK
Byte 3 to byte 6: start address
byte 3: MSB
byte 6: LSB
Byte 7:
3.6
checksum: XOR (byte 3, byte 4, byte 5, byte 6)
Write Memory command
The Write Memory command is used to write data to any valid memory address (see note
below) i.e. RAM, Flash memory, option byte area...
When the bootloader receives the Write Memory command, it transmits the ACK byte to the
application. After the transmission of the ACK byte, the bootloader waits for an address (4
bytes, byte 1 is the address MSB and byte 4 is the LSB) and a checksum byte, it then
checks the received address. For the Option byte area, the start address must be the base
address of the Option byte area (see note) to avoid writing inopportunely in this area.
If the received address is valid and the checksum is correct, the bootloader transmits an
ACK byte, otherwise it transmits a NACK byte and aborts the command. When the address
is valid and the checksum is correct, the bootloader:
•
gets a byte, N, which contains the number of data bytes to be received
•
receives the user data ((N + 1) bytes) and the checksum (XOR of N and of all data
bytes)
•
programs the user data to memory starting from the received address
•
at the end of the command, if the write operation was successful, the bootloader
transmits the ACK byte; otherwise it transmits a NACK byte to the application and
aborts the command
The maximum length of the block to be written for the STM32 is 256 bytes.
If the Write Memory command is issued to the Option byte area, all options are erased
before writing the new values, and at the end of the command the bootloader generates a
system Reset to take into account the new configuration of the option byte.
Note:
When writing to the RAM, you should take care not to overlap the first RAM memory used
by the bootloader firmware.
No error is returned when performing write operations on write-protected sectors.No error is
returned when the start address is invalid.
18/37
DocID17066 Rev 6
AN3155
Bootloader command set
Figure 12. Write Memory command: host side
3TART7-
3ENDXX#%
7AITFOR!#+
OR.!#+
.!#+
!#+
3ENDTHESTARTADDRESSBYTES
CHECKSUM
7AITFOR!#+
OR.!#+
.!#+
!#+
3ENDTHENUMBEROFBYTESTOBEWRITTEN
BYTETHEDATA.BYTES
ANDCHECKSUM
7AITFOR!#+
OR.!#+
.!#+
!#+
%NDOF7- AIB
1. WM = Write Memory.
2. N+1 should always be a multiple of 4.
Note:
Some products may return two NACKs instead of one single NACK when Read Protection
(RDP) is active (or Read Potection level 1 is active). To know if a given product returns one
single NACK or two NACKs in this situation, please refer to the known limitations section
relative to that product in AN2606.
DocID17066 Rev 6
19/37
Bootloader command set
AN3155
Figure 13. Write Memory command: device side
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ŶĚŽĨtD;ϭͿ
1. WM = Write Memory.
2. N+1 should always be a multiple of 4.
20/37
DocID17066 Rev 6
ĂŝϭϰϲϰϮĞ
AN3155
Bootloader command set
The host sends the bytes to the STM32 as follows:
Byte 1:
0x31
Byte 2:
0xCE
Wait for ACK
Byte 3 to byte 6: start address
byte 3: MSB
byte 6: LSB
Byte 7:
Checksum: XOR (Byte3, Byte4, Byte5, Byte6)
Wait for ACK
Byte 8:
Number of bytes to be received (0 < N ≤ 255)
N +1 data bytes:(Max 256 bytes)
Checksum byte: XOR (N, N+1 data bytes)
3.7
Erase Memory command
The Erase Memory command allows the host to erase Flash memory pages. When the
bootloader receives the Erase Memory command, it transmits the ACK byte to the host.
After the transmission of the ACK byte, the bootloader receives one byte (number of pages
to be erased), the Flash memory page codes and a checksum byte; if the checksum is
correct then bootloader erases the memory and sends an ACK byte to the host, otherwise it
sends a NACK byte to the host and the command is aborted.
Erase Memory command specifications:
Note:
1.
the bootloader receives one byte that contains N, the number of pages to be erased –
1.
N = 255 is reserved for global erase requests. For 0 ≤ N ≤ 254, N + 1 pages are erased.
2.
the bootloader receives (N + 1) bytes, each byte containing a page number
No error is returned when performing erase operations on write protected sectors.
DocID17066 Rev 6
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Bootloader command set
AN3155
Figure 14. Erase Memory command: host side
6WDUW(5
6HQG[[%&
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1$&.
$&.
(QGRI(5
DLE
1. ER = Erase Memory.
22/37
DocID17066 Rev 6
AN3155
Bootloader command set
Figure 15. Erase Memory command: device side
3TART%2
.O
2ECEIVEDBYTES
XX"#
9ES
2$0ACTIVE
9ES
.O
3END!#+BYTE
2ECEIVETHENUMBEROFPAGES
TOBEERASEDBYTE
9ES
X&&RECEIVED
.O
2ECEIVETHEPAGECODES
9ES
3TART'LOBAL%RASE
-ASS%RASE
.O
2ECEIVETHECHECKSUM
#HECKSUM
/+
.O
9ES
%RASETHECORRESPONDINGPAGES
3END!#+BYTE
3END.!#+BYTE
%NDOF%2
AIC
1. ER = Erase Memory.
Note:
After sending the erase memory command and its checksum, if the host sends 0xFF
followed by data different from 0x00, the mass erase is not performed but an ACK is send
by the device.
The host sends bytes to the STM32 as follows:
Byte 1: 0x43
Byte 2: 0xBC
Wait for ACK
Byte 3: 0xFF or number of pages to be erased – 1 (0 ≤ N ≤ maximum number of pages)
DocID17066 Rev 6
23/37
Bootloader command set
AN3155
Byte 4: 0x00 (in case of global erase) or ((N + 1 bytes (page numbers) and then checksum
XOR (N, N+1 bytes))
3.8
Extended Erase Memory command
The Extended Erase Memory command allows the host to erase Flash memory pages using
two bytes addressing mode. When the bootloader receives the Extended Erase Memory
command, it transmits the ACK byte to the host. After the transmission of the ACK byte, the
bootloader receives two bytes (number of pages to be erased), the Flash memory page
codes (each one coded on two bytes, MSB first) and a checksum byte (XOR of the sent
bytes); if the checksum is correct, the bootloader erases the memory and sends an ACK
byte to the host. Otherwise it sends a NACK byte to the host and the command is aborted.
Extended Erase Memory command specifications:
1.
The bootloader receives one half-word (two bytes) that contain N, the number of pages
to be erased:
a)
For N = 0xFFFY (where Y is from 0 to F) special erase is performed:
- 0xFFFF for global mass erase
- 0xFFFE for bank 1 mass erase
- 0xFFFD for bank 2 mass erase
- Codes from 0xFFFC to 0xFFF0 are reserved
b)
2.
For other values where 0 ≤ N < maximum number of pages: N + 1 pages are
erased.
The bootloader receives:
a)
In the case of a special erase, one byte: checksum of the previous bytes:
- 0x00 for 0xFFFF
- 0x01 for 0xFFFE
- 0x02 for 0xFFFD
a)
Note:
In the case of N+1 page erase, the bootloader receives (2 x (N + 1)) bytes, each
half-word containing a page number (coded on two bytes, MSB first). Then all
previous byte checksums (in one byte).
No error is returned when performing erase operations on write-protected sectors.
The maximum number of pages is relative to the product and thus should be respected.
24/37
DocID17066 Rev 6
AN3155
Bootloader command set
Figure 16. Extended Erase Memory command: host side
6WDUW((5
6HQG[[%%
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1$&.
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E\WHV
:DLWIRU$&.RU1$&.
1$&.
$&.
(QGRI((5
AI
1. EER = Extended Erase Memory
DocID17066 Rev 6
25/37
Bootloader command set
AN3155
Figure 17. Extended Erase Memory command: device side
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ďLJƚĞƐĞĂĐŚ͕D^ĨŝƌƐƚͿ
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^ĞŶĚE<ďLJƚĞ
ƌĂƐĞƚŚĞĐŽƌƌĞƐƉŽŶĚŝŶŐƉĂŐĞƐ
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ĂŝϭϳϰϲϭĐ
1. EER = Extended Erase Memory.
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DocID17066 Rev 6
AN3155
Bootloader command set
The host sends the bytes to the STM32F1xxx as follows:
Byte 1:
0x44
Byte 2:
0xBB
Wait for ACK
Bytes 3-4:
- Special erase (0xFFFF, 0xFFFE or 0xFFFD)
OR
- Number of pages to be erased (N+1 where: 0 ≤ N < Maximum number of
pages).
Remaining
bytes
- Checksum of Bytes 3-4 in case of special erase (0x00 if 0xFFFFor 0x01
if 0xFFFE or 0x02 if 0xFFFD).
OR
- (2 x (N + 1)) bytes (page numbers coded on two bytes MSB first) and
then the checksum for bytes 3-4 and all the following bytes)
3.9
Write Protect command
The Write Protect command is used to enable the write protection for some or all Flash
memory sectors. When the bootloader receives the Write Protect command, it transmits the
ACK byte to the host. After the transmission of the ACK byte, the bootloader waits for the
number of bytes to be received (sectors to be protected) and then receives the Flash
memory sector codes from the application.
At the end of the Write Protect command, the bootloader transmits the ACK byte and
generates a system Reset to take into account the new configuration of the option byte.
Note:
Refer to STM32 product datasheets and to the “STM32 microcontroller system memory
boot mode” application note (AN2606) for more details about the sector size for the device
you are using.
The Write Protect command sequence is as follows:
Note:
•
the bootloader receives one byte that contains N, the number of sectors to be writeprotected – 1 (0 ≤ N ≤ 255)
•
the bootloader receives (N + 1) bytes, each byte contains a sector code
The total number of sectors and the sector number to be protected are not checked, this
means that no error is returned when a command is passed with a wrong number of sectors
to be protected or a wrong sector number.
If a second Write Protect command is executed, the Flash memory sectors that had been
protected by the first command become unprotected and only the sectors passed within the
second Write Protect command become protected.
DocID17066 Rev 6
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Bootloader command set
AN3155
Figure 18. Write Protect command: host side
6WDUW:3
6HQG[[&
1$&.
:DLWIRU$&.
RU1$&.
$&.
6HQGWKHQXPEHURIVHFWRUV
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6HQGFKHFNVXP
:DLWIRU$&.
RU1$&.
1$&.
$&.
(QGRI:3
DLE
1. WP = Write Protect.
28/37
DocID17066 Rev 6
AN3155
Bootloader command set
Figure 19. Write Protect command: device side
3TART70
.O
2ECEIVEDBYTES
XX#
9ES
2$0ACTIVE
9ES
.O
3END!#+BYTE
2ECEIVETHENUMBEROFSECTORS
TOBEPROTECTEDBYTE
2ECEIVETHESECTORCODES
2ECEIVETHECHECKSUM
#HECKSUM
/+
.O
9ES
7RITEPROTECTTHEREQUESTEDSECTORS
3END!#+BYTE
3END.!#+BYTE
'ENERATESYSTEMRESET
%NDOF70
AIC
1. WP = Write Protect.
DocID17066 Rev 6
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Bootloader command set
3.10
AN3155
Write Unprotect command
The Write Unprotect command is used to disable the write protection of all the Flash
memory sectors. When the bootloader receives the Write Unprotect command, it transmits
the ACK byte to the host. After the transmission of the ACK byte, the bootloader disables
the write protection of all the Flash memory sectors. After the unprotection operation the
bootloader transmits the ACK byte.
At the end of the Write Unprotect command, the bootloader transmits the ACK byte and
generates a system Reset to take into account the new configuration of the option byte.
Figure 20. Write Unprotect command: host side
6WDUW:381
6HQG[[&
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RU1$&.
1$&.
$&.
:DLWIRU$&.
RU1$&.
1$&.
$&.
(QGRI:381
DL
1. WPUN = Write Unprotect.
30/37
DocID17066 Rev 6
AN3155
Bootloader command set
Figure 21. Write Unprotect command: device side
3TART705.
.O
2ECEIVEDBYTES
XX#
9ES
2$0ACTIVE
9ES
.O
3END!#+BYTE
2EMOVETHEPROTECTIONFORTHE
ENTIRE&LASHMEMORY
3END!#+BYTE
3END.!#+BYTE
'ENERATESYSTEMRESET
%NDOF705.
AIC
1. WPUN = Write Unprotect.
3.11
Readout Protect command
The Readout Protect command is used to enable the Flash memory read protection. When
the bootloader receives the Readout Protect command, it transmits the ACK byte to the
host. After the transmission of the ACK byte, the bootloader enables the read protection for
the Flash memory.
At the end of the Readout Protect command, the bootloader transmits the ACK byte and
generates a system Reset to take into account the new configuration of the option byte.
DocID17066 Rev 6
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Bootloader command set
AN3155
Figure 22. Readout Protect command: host side
6WDUW5'3B350
6HQG[['
:DLWIRU$&.
RU1$&.
1$&.
$&.
:DLWIRU$&.
RU1$&.
1$&.
$&.
(QGRI5'3B350
DL
1. RDP_PRM = Readout Protect.
Figure 23. Readout Protect command: device side
3TART2$0?02-
.O
2ECEIVEDBYTES
XX$
9ES
2$0ACTIVE
9ES
.O
3END!#+BYTE
!CTIVATE2EADPROTECTIONFOR&LASH
MEMORY
3END!#+BYTE
3END.!#+BYTE
'ENERATESYSTEMRESET
%NDOF2$0?02-
AIC
1. RDP_PRM = Readout Protect.
32/37
DocID17066 Rev 6
AN3155
3.12
Bootloader command set
Readout Unprotect command
The Readout Unprotect command is used to disable the Flash memory read protection.
When the bootloader receives the Readout Unprotect command, it transmits the ACK byte
to the host. After the transmission of the ACK byte, the bootloader erases all the Flash
memory sectors and it disables the read protection for the entire Flash memory. If the erase
operation is successful, the bootloader deactivates the RDP.
If the erase operation is unsuccessful, the bootloader transmits a NACK and the read
protection remains active.
At the end of the Readout Unprotect command, the bootloader transmits an ACK and
generates a system Reset to take into account the new configuration of the option byte.
Note:
For most STM32 products, the readout unprotect operation induce a mass erase of the flash
memory, so the Host has to wait sufficient time after the second ACK and before restarting
connection. To know how much time this operation takes, please refer to the mass erase
time in the product datasheet (when relevant).
Figure 24. Readout Unprotect command: host side
6WDUW5'8B350
6HQG[['
:DLWIRU$&.
RU1$&.
1$&.
$&.
:DLWIRU$&.
RU1$&.
1$&.
$&.
(QGRI5'8B350
AI
1. RDU_PRM = Readout Unprotect.
DocID17066 Rev 6
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Bootloader command set
AN3155
Figure 25. Readout Unprotect command: device side
3TART2$5?02-
2ECEIVEDBYTES
XX$
.O
9ES
3END!#+BYTE
$ISABLE2$0
3END!#+BYTE
#LEARALL2!-MEMORY
'ENERATESYSTEMRESET
%NDOF2$5?02-
2. RDU_PRM = Readout Unprotect.
34/37
DocID17066 Rev 6
3END.!#+BYTE
AIB
AN3155
4
Bootloader protocol version evolution
Bootloader protocol version evolution
Table 3 lists the bootloader versions.
Table 3. Bootloader protocol versions
Version
Description
V2.0
Initial bootloader version.
V2.1
– Update Go command to initialize the main stack pointer
– Update Go command to return NACK when jump address is in
the Option byte area or System memory area
– Update Get ID command to return the device ID on two bytes
– Update the bootloader version to V2.1
V2.2
– Update Read Memory, Write Memory and Go commands to
deny access, with a NACK response, to the first bytes of RAM
memory used by the bootloader
– Update Readout Unprotect command to initialize the whole RAM
content to 0x0 before RDP disable operation
V3.0
– Extended Erase command added to support number of pages
larger than 256 and separate bank mass erase.
– Erase command has not been modified in this version but, due to
addition of the Extended Erase command it is no longer
supported (Erase and Extended Erase commands are
exclusive).
V3.1
– Limitation fix of:
“When a Read Memory command or Write Memory command is
issued with an unsupported memory address and a correct
address checksum (ie. address 0x6000 0000), the command is
aborted by the bootloader device, but the NACK (0x1F) is not
sent to the host. As a result, the next 2 bytes (which are the
number of bytes to be read/written and its checksum) are
considered as a new command and its checksum.” (1)
No changes in specification, the product implementation has
been corrected.
1.
If the “number of data - 1” (N-1) to be read/written is not equal to a valid command code (0x00, 0x01,
0x02, 0x11, 0x21, 0x31, 0x43, 0x44, 0x63, 0x73, 0x82 or 0x92), then the limitation is not perceived from
the host since the command is NACKed anyway (as an unsupported new command).
DocID17066 Rev 6
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Revision history
5
AN3155
Revision history
Table 4. Document revision history
Date
Revision
09-Mar-2010
1
Initial release.
2
Table 2: USART bootloader commands: added Extended Erase
command; removed footnote 2 concerning read protection from the
Readout Protect command.
Communication safety: amended Note 1.
Section 3.1: Get command: updated byte 10.
Updated Figure 10: Go command: host side for missing ACK state.
Section 3.7: Write Memory command: added Note 1 and Note 2.
Figure 12, and Figure 13: added notes regarding N+1.
Added Section 3.8: Extended Erase Memory command.
Table 3: Bootloader protocol versions: added v3.0.
3
Added Note:, Note and Note:.
Changed all occurences of “ROP” by “RDP” including in figures:
Figure 9., Figure 11., Figure 13., Figure 15., Figure 17., Figure 19.,
Figure 21., Figure 23., Figure 25..
Added Table 1: Applicable products.
26-Mar-2013
4
Added Version 3.1 in Table 3: Bootloader protocol versions.
Updated “byte 4” value in Section 3.3: Get ID command.
Replaced “address” by “ID” in this Note 1.
Replaced “End of EER” by “End of Go” in Figure 10: Go command:
host side.
Updated first sentence in Section 3.7: Write Memory command.
Removed “& address=0x1FFF F800” and replaced the two tests
“Flash memory address?” and “RAM address?” by a single test in
Figure 13: Write Memory command: device side.
Precised missing “Y” values in the third test of Figure 17: Extended
Erase Memory command: device side.
Added this Note: above Figure 24: Readout Unprotect command:
host side.
22-May-2013
5
Replaced “STM32L151xx, STM32L152xx and STM32L162xx” by
“STM32L1 Series” in Table 1: Applicable products.
6
Updated Table 1: Applicable products.
Removed note 4 and added Note 3.in Table 2: USART bootloader
commands.
Removed section 3.1 Device-dependent bootloader parameters.
Updated Figure 10: Go command: host side and Figure 11: Go
command: device side.
Updated Section 3.6: Write Memory command.
20-Apr-2010
12-Feb-2013
20-Jun-2014-
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Changes
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