HT85F2270 datasheet(142/226 Pages) HOLTEK

142 / 226 page

Rev. 1.00

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Standard 8051 8-Bit Flash MCU

HT85F2260/HT85F2270/HT85F2280

Timer 2 with PCA

Time 2 and 4-channel PCA modules provide the Compare, Reload, Capture and programmable

clock output functions. Each of the four Timer 2 Modules contains a pair of registers, CRCL/CRCH

for Module 0 and CCLn/CCHn for Modules 1, 2 and 3. These registers are compared with the

Timer 2 TL2/TH2 register pair and when a compare match occurs, an interrupt signal can be

generated. The value in the Timer 2 registers increases by one each time an internal clock pulse is

received or an external transition occurs on the external timer pin.

The Compare function provides two modes, Mode 0 and Mode 1. When a compare match takes

place, the compare results will output to the respective output pins, according to the selected mode.

Refer Compare mode section for details.

There are two modes for the Capture function, Mode 0 and Mode 1, which are used to select

different trigger methods. In Mode 0, the Capture function is triggered by the external I/O pins,

CCn. In Mode 1, the Capture function is triggered by writing data to the CCLn or CRCL registers.

Once the Capture function is enabled and triggered, the Timer 2 data in the TL2 and TH2 registers

will be captured into the respective CCLn/CCHn or CRCL/CRCH registers. Refer Capture modes

for details.

In the Reload mode, the timer counter registers, TH2 and TL2, are located in the Special Function

Registers and is the place where the actual timer value is stored. The value in the timer registers

increases by one each time an internal clock pulse is received or an external transition occurs on

the external timer pin. The timer will count from the initial value loaded by the preload register to

the full count of FFFFH for the 16-bit Timer/Event Counters, at which point the timer overflows

and an internal interrupt signal is generated. There are two modes to reload the CRC register data,

one is the counter overflow and the other is triggered by the falling edge on the T2EX pin. Refer

Reload mode for details.

In the Programmable Clock Output mode, the clock output frequency depends on the system

clock and the reload value of the Timer 2 capture registers, CRCH and CRCL. The output clock

is generated by programming the T2CON control bit, and output via T2 pin. Refer Programmable

Clock Output mode for details.

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