ST10F276E datasheet(55/235 Pages) STMICROELECTRONICS

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ST10F276E

Bootstrap loader

Doc ID 12303 Rev 3

55/235

Figure 9.

UART bootstrap loader sequence

BSL initialization time, > 1ms @ fCPU = 40 MHz

Zero byte (1 start bit, eight ‘0’ data bits, 1 stop bit), sent by host

Acknowledge byte, sent by ST10F276E

32 bytes of code / data, sent by host

Caution: TxD0 is only driven a certain time after reception of the zero byte (1.3ms @ fCPU = 40 MHz).

Internal Boot ROM / Test-Flash

5.3.2

Entering bootstrap via UART

The ST10F276E enters BSL mode if pin P0L.4 is sampled low at the end of a hardware

reset. In this case, the built-in bootstrap loader is activated independently of the selected

bus mode. The bootstrap loader code is stored in a special Test-Flash; no part of the

standard mask ROM or Flash memory area is required for this.

After entering BSL mode and the respective initialization, the ST10F276E scans the RxD0

line to receive a zero byte, that is, 1 start bit, eight ‘0’ data bits and 1 stop bit. From the

duration of this zero byte, it calculates the corresponding baud rate factor with respect to the

current CPU clock, initializes the serial interface ASC0 accordingly and switches pin TxD0 to

output. Using this baud rate, an acknowledge byte is returned to the host that provides the

loaded data.

The acknowledge byte is D5h for the ST10F276E.

ST10F276E 데이터시트(PDF) 55 Page - STMicroelectronics