STMicroelectronics SPC572L series Reference Manual page 1871

RM0400
enabling software to assert a signal to an external device pin to notify an external tool that
data is available. The tool can then retrieve the data.
In this type of application the DTS_SEMAPHORE register and DTS Trigger Output (DTO)
signal provide a mechanism to notify the calibration tool that the calibration variable or
variables (or sets of measurements), up to 32, have been updated with new values and are
available for the tool to access.
Note: It is the user's responsibility to ensure that the tool has time to retrieve the data prior to that
particular trigger being set a second time. It is also permissible to have multiple triggers
active at the same time or for a second trigger to be set before a previous trigger has been
serviced, as long as it is not the same trigger (unless it is acceptable to the tool to not
receive every data set).
Figure 1110
acquisition system. The startup and synchronization sequence can be as simple or as
complicated as the need requires. However, a typical startup sequence is as follows:
1. The DTS_STARTUP register is cleared by a power on reset or any CPU reset.
2. The tool writes a non-zero value to the DTS_STARTUP register.
3. The CPU (user application software) then reads the value of the DTS_STARTUP
register. Based on this value, different initialization options can be selected. The bits
can be used for any application specific definitions.
4. Since the DTS_SEMAPHORE register is cleared when the tool reads the current value.
The tool should perform all necessary initialization before reading this register. The
application software can then check that the DTS_SEMAPHORE register was cleared
by the tool, to determine that it is safe to start using it for its intended raster trigger
semaphore function.
5. An optional hand shake from the CPU can be used to inform the tool that the user
software has detected that the tool is attached and the CPU has performed the proper
initialization for the tool by writing a predefined value to the DTS_SEMAPHORE
register (the example shown in the figure above uses 0xAAAA_AAAA—all A's was
used since it is unrealistic that 16 channels could be enabled very quickly after start up
after a reset).
shows an example DTS startup sequence for an external real-time data
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Development Trigger Semaphore (DTS)
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