HT68F03 datasheet(120/139 Pages) HOLTEK

120 / 139 page

HT66F03/HT66F04/HT68F03/HT68F04

Rev. 1.00

120

April 16, 2010

Power Down Mode and Wake-up

Entering the IDLE or SLEEP Mode

There is only one way for the device to enter the SLEEP

or IDLE Mode and that is to execute the

²HALT² instruc-

tion in the application program. When this instruction is

executed, the following will occur:

· The system clock will be stopped and the application

program will stop at the

²HALT² instruction.

· The Data Memory contents and registers will maintain

their present condition.

· The WDT will be cleared and resume counting if the

WDT clock source is selected to come from the fSUB

clock source and the WDT is enabled. The WDT will

stop if its clock source originates from the system clock.

· The I/O ports will maintain their present condition.

· In the status register, the Power Down flag, PDF, will be

set and the Watchdog time-out flag, TO, will be cleared.

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, there are other considerations

which must also be taken into account by the circuit de-

signer 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 con-

nected 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 de-

vices which have different package types, as there may

be unbonbed pins. These must either be setup as out-

puts 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 out-

puts. 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 required if the configuration options have enabled

the LIRC oscillator.

Wake-up

After the system enters the SLEEP or IDLE Mode, it can

be woken up from one of various sources listed as follows:

· An external reset

· An external falling edge on Port A

· A system interrupt

· A WDT overflow

If the system is woken up by an external reset, the de-

vice will experience a full system reset, however, if the

device is woken up by a WDT overflow, a Watchdog

Timer reset will be initiated. Although both of these

wake-up methods will initiate a reset operation, the ac-

tual source of the wake-up can be determined by exam-

ining the TO and PDF flags. The PDF flag is cleared by a

system power-up or executing the clear Watchdog

Timer instructions and is set when executing the

²HALT²

instruction. The TO flag is set if a WDT time-out occurs,

and causes a wake-up that only resets the Program

Counter and Stack Pointer, the other flags remain in

their original status.

Each pin on Port A can be setup using the PAWU regis-

ter to permit a negative transition on the pin to wake-up

the system. When a Port A pin wake-up occurs, the pro-

gram will resume execution at the instruction following

the

²HALT² instruction.

If the system is woken up by an interrupt, then two possi-

ble 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 exe-

cution at the instruction following the

²HALT² instruction.

In this situation, the interrupt which woke-up the device

will not be immediately serviced, but will rather be ser-

viced 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 func-

tion of the related interrupt will be disabled.

HT68F03 Datasheet(PDF) 120 Page - Holtek Semiconductor Inc

HT68F03 Datasheet(HTML) 120 Page - Holtek Semiconductor Inc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL