ST72361J4-Auto datasheet(105/279 Pages) STMICROELECTRONICS

105 / 279 page

ST72361xx-Auto

16-bit timer

Doc ID 12468 Rev 3

105/279

The user must read the MS Byte first, then the LS Byte value is buffered automatically.

This buffered value remains unchanged until the 16-bit read sequence is completed, even if

the user reads the MS Byte several times.

After a complete reading sequence, if only the CLR register or ACLR register are read, they

return the LS Byte of the count value at the time of the read.

Whatever the timer mode used (input capture, output compare, One Pulse mode or PWM

mode) an overflow occurs when the counter rolls over from FFFFh to 0000h then:

●

The TOF bit of the SR register is set.

●

A timer interrupt is generated if:

–

TOIE bit of the CR1 register is set and

–

I bit of the CC register is cleared.

If one of these conditions is false, the interrupt remains pending to be issued as soon as

they are both true.

Clearing the overflow interrupt request is done in two steps:

Reading the SR register while the TOF bit is set.

An access (read or write) to the CLR register.

Note:

The TOF bit is not cleared by accesses to ACLR register. The advantage of accessing the

ACLR register rather than the CLR register is that it allows simultaneous use of the overflow

function and reading the free running counter at random times (for example, to measure

elapsed time) without the risk of clearing the TOF bit erroneously.

The timer is not affected by WAIT mode.

In HALT mode, the counter stops counting until the mode is exited. Counting then resumes

from the previous count (MCU awakened by an interrupt) or from the reset count (MCU

awakened by a Reset).

12.3.2

External clock

The external clock (where available) is selected if CC0 = 1 and CC1 = 1 in the CR2 register.

The status of the EXEDG bit in the CR2 register determines the type of level transition on

the external clock pin EXTCLK that will trigger the free running counter.

The counter is synchronized with the falling edge of the internal CPU clock.

A minimum of four falling edges of the CPU clock must occur between two consecutive

active edges of the external clock; thus the external clock frequency must be less than a

quarter of the CPU clock frequency.

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