HT68FU50 datasheet(135/244 Pages) HOLTEK

135 / 244 page

HT68F20/HT68F30/HT68F40/HT68F50/HT68F60

HT68FU30/HT68FU40/HT68FU50/HT68FU60

Rev. 1.50

135

March 15, 2011

Comparators

Two independent analog comparators are contained

within these devices. These functions offer flexibility via

their register controlled features such as power-down,

polarity select, hysteresis etc. In sharing their pins with

normal I/O pins the comparators do not waste precious

I/O pins if there functions are otherwise unused.

Comparator Operation

The device contains two comparator functions which

are used to compare two analog voltages and provide

an output based on their difference. Full control over the

two internal comparators is provided via two control reg-

isters, CP0C and CP1C, one assigned to each com-

parator. The comparator output is recorded via a bit in

their respective control register, but can also be trans-

ferred out onto a shared I/O pin. Additional comparator

functions include, output polarity, hysteresis functions

and power down control.

Any pull-high resistors connected to the shared com-

parator input pins will be automatically disconnected

when the comparator is enabled. As the comparator in-

puts approach their switching level, some spurious out-

put signals may be generated on the comparator output

due to the slow rising or falling nature of the input sig-

nals. This can be minimised by selecting the hysteresis

function will apply a small amount of positive feedback

to the comparator. Ideally the comparator should switch

at the point where the positive and negative inputs sig-

nals are at the same voltage level, however, unavoid-

able input offsets introduce some uncertainties here.

The hysteresis function, if enabled, also increases the

switching offset value.

Comparator Registers

There are two registers for overall comparator opera-

tion, one for each comparator. As corresponding bits in

the two registers have identical functions, they following

C n +

C n -

C n P O L

C n O U T

C n X

C n S E L

Comparator

Name

Bit

76543210

CP0C

C0SEL

C0EN

C0POL

C0OUT

C0OS

¾¾

C0HYEN

CP1C

C1SEL

C1EN

C1POL

C1OUT

C1OS

¾¾

C1HYEN

Comparator Registers List

Comparator Interrupt

Each also possesses its own interrupt function. When

any one of the changes state, its relevant interrupt flag

will be set, and if the corresponding interrupt enable bit

is set, then a jump to its relevant interrupt vector will be

executed. Note that it is the changing state of the

C0OUT or C1OUT bit and not the output pin which gen-

erates an interrupt. If the microcontroller is in the SLEEP

or IDLE Mode and the Comparator is enabled, then if the

external input lines cause the Comparator output to

change state, the resulting generated interrupt flag will

also generate a wake-up. If it is required to disable a

wake-up from occurring, then the interrupt flag should

be first set high before entering the SLEEP or IDLE

Mode.

Programming Considerations

If the comparator is enabled, it will remain active when

the microcontroller enters the SLEEP or IDLE Mode,

however as it will consume a certain amount of power,

the user may wish to consider disabling it before the

SLEEP or IDLE Mode is entered.

As comparator pins are shared with normal I/O pins the

I/O registers for these pins will be read as zero (port con-

trol register is

²1²) or read as port data register value

(port control register is

²0²) if the comparator function is

enabled.

HT68FU50 数据表(PDF) 135 Page - Holtek Semiconductor Inc

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