Rev. 1.10
72
October 23, 2020
Rev. 1.10
73
October 23, 2020
BC66F5652
2.4GHz RF Transceiver A/D Flash MCU
BC66F5652
2.4GHz RF Transceiver A/D Flash MCU
possible situations may occur. The first is where the related interrupt is disabled or the interrupt
is enabled but the stack is full, in which case the program will resume execution at the instruction
following the “HALT” instruction. In this situation, the interrupt which woke up the device will not
be immediately serviced, but will rather be serviced later when the related interrupt is finally enabled
or when a stack level becomes free. The other situation is where the related interrupt is enabled and
the stack is not full, in which case the regular interrupt response takes place. If an interrupt request
flag is set high before entering the SLEEP or IDLE Mode, the wake-up function of the related
interrupt will be disabled.
Programming Considerations
The HXT and LXT oscillators use different SST counter. For example, if the system is woken up
from the SLEEP Mode and both the HXT and LXT oscillators need to start-up from an off state.
• If the device is woken up from the SLEEP Mode to the FAST Mode, the high speed system
oscillator needs an SST period. The device will execute first instruction after H
IRCF/HXTF is
“1”. At this time, the LXT oscillator may not be stability if f
SUB
is from the LXT oscillator. The
same situation occurs in the power-on state. The LXT oscillator is not ready yet when the first
instruction is executed.
• There are peripheral functions, such as TMs, for which the f
SYS
is used. If the system clock source
is switched from f
H
to f
SUB
, the clock source to the peripheral functions mentioned above will
change accordingly.
Watchdog Timer
The Watchdog Timer is provided to prevent program malfunctions or sequences from jumping to
unknown locations, due to certain uncontrollable external events such as electrical noise.
Watchdog Timer Clock Source
The Watchdog Timer clock source is provided by the internal clock, f
LIRC
which is sourced from
the LIRC oscillator. The LIRC internal oscillator has an approximate frequency of 32kHz and this
specified internal clock period can vary with V
DD
, temperature and process variations. The Watchdog
Timer source clock is then subdivided by a ratio of 2
8
to 2
18
to give longer timeouts, the actual value
being chosen using the WS2~WS0 bits in the WDTC register.
Watchdog Timer Control Register
A single register, WDTC, controls the required timeout period as well as the enable/disable and reset
MCU operation.
• WDTC Register
Bit
7
6
5
4
3
2
1
0
Name
WE4
WE3
WE2
WE1
WE0
WS2
WS1
WS0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
POR
0
1
0
1
0
0
1
1
Bit 7~3
WE4~WE0
: WDT function software control
10101: Disable
01010: Enable
Other values: Reset MCU
When these bits are changed to any other values due to environmental noise the
microcontroller will be reset; this reset operation will be activated after a delay time,
t
SRESET
, and the WRF bit in the CTRL register will be set high.