ST10F276Z5 datasheet(59/239 Pages) STMICROELECTRONICS

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ST10F276Z5

Bootstrap loader

59/239

The Bootstrap Loader can load

●

the complete application software into ROM-less systems,

●

temporary software into complete systems for testing or calibration,

●

a programming routine for Flash devices.

The BSL mechanism may be used for standard system start-up as well as for only special

occasions like system maintenance (firmware update) or end-of-line programming or

testing.

5.4.2

Entering the CAN bootstrap loader

The ST10F276Z5 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 device scans the CAN1_TxD

line to receive the following initialization frame:

●

Standard identifier = 0h

●

DLC = 0h

As all the bits to be transmitted are dominant bits, a succession of 5 dominant bits and 1

stuff bit on the CAN network is used. From the duration of this frame, it calculates the

corresponding baud rate factor with respect to the current CPU clock, initializes the CAN1

interface accordingly, switches pin CAN1_TxD to output and enables the CAN1 interface to

take part in the network communication. Using this baud rate, a Message Object is

configured in order to send an acknowledge frame. The device does not send this Message

Object but the host can request it by sending a remote frame.

The acknowledge frame is the following for the ST10F276Z5:

●

Standard identifier = E6h

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DLC = 3h

●

Data0 = D5h, that is, generic acknowledge of the ST10 devices

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Data1 = IDCHIP least significant byte

●

Data2 = IDCHIP most significant byte

For the ST10F276Z5, IDCHIP is set to 114Xh.

Note:

Two behaviors can be distinguished in ST10 acknowledging to the host. If the host is

behaving according to the CAN protocol, as at the beginning the ST10 CAN is not

configured, the host is alone on the CAN network and does not receive an acknowledge. It

automatically sends again the zero frame. As soon as the ST10 CAN is configured, it

acknowledges the zero frame. The “acknowledge frame” with identifier 0xE6 is configured,

but the Transmit Request is not set. The host can request this frame to be sent and therefore

obtains the IDCHIP by sending a remote frame.

Hint: As the IDCHIP is sent in the acknowledge frame, Flash programming software now

can immediately identify the exact type of device to be programmed.

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