ST10F276Z5 datasheet(61/239 Pages) STMICROELECTRONICS

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ST10F276Z5

Bootstrap loader

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mode. Most probably the initially loaded routine will load additional code or data, as an

average application is likely to require substantially more than 64 instructions. This second

receive loop may directly use the pre-initialized CAN interface to receive data and store it in

arbitrary user-defined locations.

This second level of loaded code may be

●

the final application code

●

another, more sophisticated, loader routine that adds a transmission protocol to

enhance the integrity of the loaded code or data

●

a code sequence to change the system configuration and enable the bus interface to

store the received data into external memory

This process may go through several iterations or may directly execute the final application.

In all cases the ST10F276Z5 still runs in BSL mode, that is, with the watchdog timer

disabled and limited access to the internal Flash area. All code fetches from the internal

Flash area (01’0000H ...08’FFFFH) are redirected to the special Test-Flash. Data read

operations will access the internal Flash of the ST10F276Z5.

5.4.5

Choosing the baud rate for the BSL via CAN

The Bootstrap via CAN acts the same way as in the UART bootstrap mode. When the

ST10F276Z5 is started in BSL mode, it polls the RxD0 and CAN1_RxD lines. When polling

a low level on one of these lines, a timer is launched that is stopped when the line returns to

high level.

For CAN communication, the algorithm is made to receive a zero frame, that is, the standard

identifier is 0x0, DLC is 0. This frame produces the following levels on the network: 5D, 1R,

5D, 1R, 5D, 1R, 5D, 1R, 5D, 1R, 4D, 1R, 1D, 11R. The algorithm lets the timer run until the

detection of the 5th recessive bit. This way the bit timing is calculated over the duration of 29

bit times: This minimizes the error introduced by the polling.

Figure 12.

Bit rate measurement over a predefined zero-frame

........

Start

Stuff bit

Measured time

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