Rev. 1.10
68
October 23, 2020
Rev. 1.10
69
October 23, 2020
BC66F5652
2.4GHz RF Transceiver A/D Flash MCU
BC66F5652
2.4GHz RF Transceiver A/D Flash MCU
Operating Mode Switching
The device can switch between operating modes dynamically allowing the user to select the best
performance/power ratio for the present task in hand. In this way microcontroller operations that
do not require high performance can be executed using slower clocks thus requiring less operating
current and prolonging battery life in portable applications.
In simple terms, mode switching between the FAST Mode and SLOW Mode is executed using the
CKS2~CKS0 bits in the SCC register while mode switching from the FAST/SLOW Modes to the
SLEEP/IDLE Modes is executed via the HALT instruction. When a HALT instruction is executed,
whether the device enters the IDLE Mode or the SLEEP Mode is determined by the condition of the
FHIDEN and FSIDEN bits in the SCC register.
FAST
f
SYS
=f
H
~f
H
/64
f
H
on
CPU run
f
SYS
on
f
SUB
on
SLOW
f
SYS
=f
SUB
f
SUB
on
CPU run
f
SYS
on
f
H
on/off
IDLE0
HALT instruction executed
CPU stop
FHIDEN=0
FSIDEN=1
f
H
off
f
SUB
on
IDLE1
HALT instruction executed
CPU stop
FHIDEN=1
FSIDEN=1
f
H
on
f
SUB
on
IDLE2
HALT instruction executed
CPU stop
FHIDEN=1
FSIDEN=0
f
H
on
f
SUB
off
SLEEP
HALT instruction executed
CPU stop
FHIDEN=0
FSIDEN=0
f
H
off
f
SUB
off
FAST Mode to SLOW Mode Switching
When running in the FAST Mode, which uses the high speed system oscillator, and therefore
consumes more power, the system clock can switch to run in the SLOW Mode by setting the
CKS2~CKS0 bits to “111” in the SCC register. This will then use the low speed system oscillator
which will consume less power. Users may decide to do this for certain operations which do not
require high performance and can subsequently reduce power consumption.
The SLOW Mode system clock is sourced from the LXT or LIRC oscillator determined by the FSS
bit in the SCC register and therefore requires this oscillator to be stable before full mode switching
occurs.