BS87B12A-3 Datasheet, PDF (64/224 Pages) Holtek Semiconductor Inc – Touch A/D Flash MCU with OCVP

BS87B12A-3/BS87C16A-3/BS87D20A-3
Touch A/D Flash MCU with OCVP
Entering the IDLE0 Mode
There is only one way for the device to enter the IDLE0 Mode and that is to execute the "HALT"
instruction in the application program with the IDLEN bit in the SMOD register equal to "1" and
the FSYSON bit in the CTRL register equal to "0". When this instruction is executed under the
conditions described above, the following will occur:
• The system clock will be stopped and the application program will stop at the "HALT"
instruction, but the low frequency clock fSUB will be on.
• The Data Memory contents and registers will maintain their present condition.
• The I/O ports will maintain their present conditions.
• In the status register, the Power Down flag PDF will be set, and WDT timeout flag TO will be
cleared.
• The WDT will be cleared and resume counting.
Entering the IDLE1 Mode
There is only one way for the device to enter the IDLE1 Mode and that is to execute the "HALT"
instruction in the application program with the IDLEN bit in the SMOD register is equal to "1"
and the FSYSON bit in the CTRL register equal to "1". When this instruction is executed under the
conditions described above, the following will occur:
• The system and the low frequency fSUB clocks will be on but the application program will stop at
the "HALT" instruction.
• The Data Memory contents and registers will maintain their present condition.
• The I/O ports will maintain their present conditions.
• In the status register, the Power Down flag PDF will be set, and WDT timeout flag TO will be
cleared.
• The WDT will be cleared and resume counting.
Standby Current Considerations
As the main reason for entering the SLEEP or IDLE Mode is to keep the current consumption of the
device to as low a value as possible, perhaps only in the order of several micro-amps except in the
IDLE1 Mode, there are other considerations which must also be taken into account by the circuit
designer if the power consumption is to be minimised. Special attention must be made to the I/O pins
on the device. All high-impedance input pins must be connected to either a fixed high or low level as
any floating input pins could create internal oscillations and result in increased current consumption.
This also applies to devices which have different package types, as there may be unbonded pins.
These must either be setup as outputs or if setup as inputs must have pull-high resistors connected.
Care must also be taken with the loads, which are connected to I/O pins, which are setup as outputs.
These should be placed in a condition in which minimum current is drawn or connected only to
external circuits that do not draw current, such as other CMOS inputs. Also note that additional
standby current will also be consumed if the LIRC oscillator has enabled.
In the IDLE1 Mode the system oscillator is on, if the peripheral function clock source is derived
from the high speed oscillator, the additional standby current will also be perhaps in the order of
several hundred micro-amps.
Rev. 1.20
64
December 05, 2016