HT85F2270 datasheet(170/226 Pages) HOLTEK

170 / 226 page

Rev. 1.00

170 of ��6

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Standard 8051 8-Bit Flash MCU

HT85F2260/HT85F2270/HT85F2280

33 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,

interrupt, wake-up, output path selection etc. In sharing their pins with normal I/O pins the

comparators do not waste precious I/O pins if there functions are unused. One comparator also has

the ability to reset the MCU.

Comparator Operation

Each 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 four control registers, CP0CR, CP1CR, CPHCR and CPICR. The comparator output

is recorded via a bit in their respective control register, but can also be transferred 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 comparator input pins will be automatically

disconnected when the comparator is enabled. As the comparator inputs approach their switching

level, some spurious output signals may be generated on the comparator output due to the slow

rising or falling nature of the input signals. 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 signals are at the same voltage

level, however, unavoidable input offsets introduce some uncertainties here. The hysteresis function,

if enabled, also increases the switching offset value. The Comparator Hysteresis control function

is selected by the CPHCR register. In addition, the comparator 0 provides the Comparator Output

Reset MCU function which is decided by the CP0RST and CP0RSTL bits in the CP0CR register.

CP0ON

CP0POL CP0OUT

C0OUT

MUX

CP0OS

CP0RST

Reset MCU

CP0RSTL

Interrupt

CP0HN[1:0]

CP0HP[1:0]

CP0-

CP0+

Comparator 0

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