CD00001237 datasheet(49/105 Pages) STMICROELECTRONICS

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ST6215C ST6225C

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8-BIT TIMER (Cont’d)

9.2.4 Functional Description

There are three operating modes, which are se-

lected by the TOUT and DOUT bits (see TSCR

two clocks which can be connected to the 7-bit

prescaler (fINT ÷ 12 or TIMER pin signal), and to

the output mode.

The settings for the different operating modes are

summarized Table 12.

Table 12. Timer Operating Modes

9.2.4.1 Gated Mode

(TOUT = “0”, DOUT = “1”)

In this mode, the prescaler is decremented by the

Timer clock input, but only when the signal on the

TIMER pin is held high (fINT/12 gated by TIMER

pin). See Figure 28 and Figure 29.

This mode is selected by clearing the TOUT bit in

the TSCR register (i.e. as input) and setting the

DOUT bit.

Note: In this mode, if the TIMER pin is multi-

plexed, the corresponding port control bits have to

be set in input with pull-up configuration through

the DDR, OR and DR registers. For more details,

please refer to the I/O Ports section.

Figure 28. fTIMER Clock in Gated Mode

Figure 29. Gated Mode Operation

TOUT DOUT

Timer

Function

Application

Event Counter

(input)

External counter clock

source

Gated input

(input)

External Pulse length

measurement

Output “0”

(output)

Output signal

Output “1”

(output)

generation

fPRESCALER

TIMER

fINT/12

fEXT

xx1

COUNTER VALUE

TIMER PIN

TIMER CLOCK

VALUE 1

VALUE 2

PULSE LENGTH

xx2

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