ST92T163 ST Microelectronics, ST92T163 Datasheet - Page 65

• Manufacturer Part Number: ST92T163
• Description: 8/16-BIT FULL SPEED USB MCU FOR COMPOSITE DEVICES WITH 16 ENDPOINTS
• Manufacturer: ST Microelectronics

WAKE-UP / INTERRUPT LINES MANAGEMENT UNIT (Cont’d)
Case 3: A wake-up event on the external wake-
up lines occurs during the STOP bit setting se-
quence
There are two possible cases:
1. Interrupt requests to the CPU are disabled: in
2. Interrupt requests to CPU are enabled: in this
this case the ST9 will not enter STOP mode, no
interrupt service routine will be executed and
the program execution continues from the
instruction following the STOP bit setting
sequence. The status of STOP and EX_STP
bits will be again:
The application can determine why the ST9 did
not enter STOP mode by polling the pending
bits of the external lines (at least one must be at
1).
case the ST9 will not enter STOP mode and the
interrupt service routine will be executed. The
status of STOP and EX_STP bits will be again:
The interrupt service routine can determine why
the ST9 did not enter STOP mode by polling
the pending bits of the external lines (at least
one must be at 1).
STOP = 0, EX_STP = 0
STOP = 0, EX_STP = 0
If the MCU really exits from STOP Mode, the
RCCU EX_STP bit is still set and must be reset by
software. Otherwise, if an Interrupt/DMA request
was acknowledged during the STOP bit setting se-
quence, the RCCU EX_STP bit is reset. This
means that the MCU has filtered the STOP Mode
entry request.
The WKUP-INT bit can be used by an interrupt
routine to detect and to distinguish events coming
from Interrupt Mode or from Wake-up Mode, allow-
ing the code to execute different procedures.
To exit STOP mode, it is sufficient that one of the
16 wake-up lines (not masked) generates an
event: the clock restarts after the delay needed for
the oscillator to restart.
Note: After exiting from STOP Mode, the software
can successfully reset the pending bits (edge sen-
sitive), even though the corresponding wake-up
line is still active (high or low, depending on the
Trigger Event register programming); the user
must poll the external pin status to detect and dis-
tinguish a short event from a long one (for example
keyboard input with keystrokes of varying length).
ST92163 - INTERRUPTS
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