ST7LUS5 datasheet(122/124 Pages) STMICROELECTRONICS

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Known limitations

ST7LUS5, ST7LU05, ST7LU09

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15.2.2

In-circuit programming of devices previously programmed with

Hardware Watchdog option

Description

In-circuit programming of devices configured with hardware watchdog (WDGSW bit in option

byte 1 programmed to 0) requires certain precautions (see below).

In-circuit programming uses ICC mode. In this mode, the hardware watchdog is not

automatically deactivated as one might expect. As a consequence, internal resets are

generated by the watchdog, thus preventing programming.

The device factory configuration is software watchdog so this issue is not seen with devices

that are programmed for the first time. For the same reason, devices programmed by the

user with the software watchdog option are not impacted.

The only devices impacted are those that have previously been programmed with the

hardware watchdog option.

Workaround

Devices configured with Hardware Watchdog must be programmed using a specific

programming mode that ignores the option byte settings. In this mode, an external clock,

normally provided by the programming tool, has to be used. In ST tools, this mode is called

“ICP OPTIONS DISABLED”.

Sockets on ST programming tools are controlled using “ICP OPTIONS DISABLED” mode.

Devices can therefore be reprogrammed by plugging them in the ST Programming Board

socket, whatever the watchdog configuration.

When using third-party tools, please refer to the manufacturer's documentation to check

how to access specific programming modes. If a tool does not have a mode that ignores the

option byte settings, devices programmed with the hardware watchdog option cannot be

reprogrammed using this tool.

15.2.3

In-circuit debugging with Hardware Watchdog

In-circuit debugging is impacted in the same way as in-circuit programming by the activation

of the hardware watchdog in ICC mode. Please refer to Section 15.2.2.

ST7LUS5 Datasheet(PDF) 122 Page - STMicroelectronics