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Moteur de recherche de fiches techniques de composants électroniques |
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Moteur de recherche de fiches techniques de composants électroniques |
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AN4221 Fiches technique(PDF) 7 Page - STMicroelectronics |
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AN4221 Fiches technique(HTML) 7 Page - STMicroelectronics |
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7 / 51 page  DocID024055 Rev 2 7/51 AN4221 Bootloader command set 50 No-Stretch commands No-Stretch commands allows executing Write, Erase, Write Protect, Write Unprotect, Read Protect and Read Unprotect operations without stretching I2C line while bootloader is performing the operation. These commands allows communicating with other devices on the bus while bootloader performs operation that require waiting time. The difference between these commands and the standard commands is at the end of the command: When hosts requests ACK/NACK at the end of the command, instead of stretching the I2C line, the bootloader responds with a third state which is Busy (0x76). When Host receives Busy state, it should poll again on the state and read one byte till it receives ACK or NACK response. Communication safety All communication from the programming host to the device is verified by 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. For each command, the host sends a byte and its complement (XOR = 0x00). Each packet is either accepted (ACK answer) or discarded (NACK answer): • ACK = 0x79 • NACK = 0x1F With No-Stretch commands Busy state is sent instead of ACK or NACK when an operation is ongoing: • BUSY= 0x76 Note: The host's frame can be one of the following: • Send Command frame: The host initiates communication as master transmitter, and sends two bytes to the device: command code + XOR. • Wait for ACK/NACK frame: The host initiates an I2C communication as master receiver, and receives one byte from the device: ACK or NACK or BUSY. • Receive Data frame: The host initiates an I2C communication as master receiver, and receives the response from the device. The number of received bytes depends on the command. • Send Data frame: The host initiates an I2C communication as master transmitter, and sends the needed bytes to the device. The number of transmitted bytes depends on the command. Caution: For I2C communication, a timeout mechanism is implemented which must be respected for Bootloader commands to be executed correctly. This timeout is implemented between two I2C frames in the same command. For example, for a Write memory command, a timeout is inserted between the command-sending frame and address memory-sending frame. Also, the same timeout period is inserted between two successive instances of data reception or 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. Please refer to STM32 product datasheet and AN2606: STM32 microcontroller system memory boot mode to know which memory spaces are valid for these commands. 4. No-Stretch commands are available only with I2C protocol V1.1. |
Numéro de pièce similaire - AN4221 |
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Description similaire - AN4221 |
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