ST7LITE2 datasheet(66/131 Pages) STMICROELECTRONICS

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ST7LITE2

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LITE TIMER (Cont’d)

11.3.3 Functional Description

11.3.3.1 Timebase Counter 1

The 8-bit value of Counter 1 cannot be read or

written by software. After an MCU reset, it starts

incrementing from 0 at a frequency of fOSC/32. An

overflow event occurs when the counter rolls over

from F9h to 00h. If fOSC = 8 MHz, then the time pe-

riod between two counter overflow events is 1 ms.

This period can be doubled by setting the TB bit in

the LTCSR1 register.

When Counter 1 overflows, the TB1F bit is set by

hardware and an interrupt request is generated if

the TB1IE bit is set. The TB1F bit is cleared by

software reading the LTCSR1 register.

11.3.3.2 Timebase Counter 2

Counter 2 is an 8-bit autoreload upcounter. It can

be read by accessing the LTCNTR register. After

an MCU reset, it increments at a frequency of

fOSC/32 starting from the value stored in the

LTARR register. A counter overflow event occurs

when the counter rolls over from FFh to the

LTARR reload value. Software can write a new

value at anytime in the LTARR register, this value

will be automatically loaded in the counter when

the next overflow occurs.

When Counter 2 overflows, the TB2F bit in the

LTCSR2 register is set by hardware and an inter-

rupt request is generated if the TB2IE bit is set.

The TB2F bit is cleared by software reading the

LTCSR2 register.

11.3.3.3 Input Capture

The 8-bit input capture register is used to latch the

free-running upcounter (Counter 1) 1 after a rising

or falling edge is detected on the ICAP1 pin. When

an input capture occurs, the ICF bit is set and the

LTICR1 register contains the MSB of Counter 1.

An interrupt is generated if the ICIE bit is set. The

ICF bit is cleared by reading the LTICR register.

The LTICR is a read-only register and always con-

tains the data from the last input capture. Input

capture is inhibited if the ICF bit is set.

Figure 41. Input Capture Timing Diagram.

04h

8-bit COUNTER 1

01h

fOSC/32

xxh

02h

03h

05h

06h

07h

04h

LTIC PIN

ICF FLAG

LTICR REGISTER

CLEARED

4µs

(@ 8MHz fOSC)

fCPU

BY S/W

07h

READING

LTIC REGISTER

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