COP8-REF-AM datasheet(36/83 Pages) NSC

36 / 83 page

13.0 Power Saving Features

Today, the proliferation of battery-operated applications has

placed new demands on designers to drive power consump-

tion down. Battery operated systems are not the only type of

applications demanding low power. The power budget con-

straints are also imposed on those consumer/industrial ap-

plications where well regulated and expensive power supply

costs cannot be tolerated. Such applications rely on low cost

and low power supply voltage derived directly from the

“mains” by using voltage rectifier and passive components.

Low power is demanded even in automotive applications,

due to increased vehicle electronics content. This is required

to ease the burden from the car battery. Low power 8-bit

microcontrollers supply the smarts to control battery-

operated, consumer/industrial, and automotive applications.

The device offers system designers a variety of low-power

consumption features that enable them to meet the demand-

ing requirements of today’s increasing range of low-power

applications. These features include low voltage operation,

low current drain, and power saving features such as HALT,

IDLE, and Multi-Input Wake-Up (MIWU).

This device supports three operating modes, each of which

have two power save modes of operation. The three operat-

ing modes are: High Speed, Dual Clock, and Low Speed.

Within each operating mode, the two power save modes are:

HALT and IDLE. In the HALT mode of operation, all micro-

controller activities are stopped and power consumption is

reduced to a very low level. In this device, the HALT mode is

enabled and disabled by a bit in the Option register. The

IDLE mode is similar to the HALT mode, except that certain

sections of the device continue to operate, such as: the

on-board oscillator, the IDLE Timer (Timer T0), and the Clock

Monitor. This allows real time to be maintained. During

power save modes of operation, all on board RAM, registers,

I/O states and timers (with the exception of T0) are unal-

tered.

Two oscillators are used to support the three different oper-

ating modes. The high speed oscillator refers to the oscillator

connected to CKI and the low speed oscillator refers to the

32 kHz oscillator connected to pins L0 & L1. When using L0

and L1 for the low speed oscillator, the user must ensure that

the L0 and L1 pins are configured for hi-Z input, L1 is not

using CKX on the USART, and Multi-Input Wake-up for these

pins is disabled.

A diagram of the three modes is shown in Figure 18.

13.1 POWER SAVE MODE CONTROL REGISTER

The ITMR control register allows for navigation between the

three different modes of operation. It is also used for the Idle

Timer. The register bit assignments are shown below. This

LSON

HSON

DCEN

CCK

SEL

RSVD

ITSEL2

ITSEL1

ITSEL0

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

LSON:

This bit is used to turn-on the low-speed oscilla-

tor. When LSON = 0, the low speed oscillator is

off. When LSON = 1, the low speed oscillator is

on. There is a startup time associated with this

oscillator. See the Oscillator Circuits section.

HSON:

This bit is used to turn-on the high speed oscil-

lator. When HSON = 0, the high speed oscillator

is off. When HSON = 1, the high speed oscillator

is on. There is a startup time associated with this

oscillator. See the startup time table in the Os-

cillator Circuits section.

DCEN:

This bit selects the clock source for the Idle

Timer. If this bit = 0, then the high speed clock is

the clock source for the Idle Timer. If this bit = 1,

then the low speed clock is the clock source for

the Idle Timer. The low speed oscillator must be

started and stabilized before setting this bit to a

CCKSEL: This bit selects whether the high speed clock or

low speed clock is gated to the microcontroller

core. When this bit = 0, the Core clock will be the

20006322

FIGURE 18. Diagram of Power Save Modes

COP8-REF-AM 数据表(PDF) 36 Page - National Semiconductor (TI)

COP8-REF-AM 数据表(HTML) 36 Page - National Semiconductor (TI)

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

数据表下载