C511 datasheet(21/43 Pages) SIEMENS

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C511 / C513

Semiconductor Group

Timer/ Counter 0 and 1

Timer/Counter 0 and 1 can be used in four operating modes as listed in table 7:

Table 7

Timer/Counter 0 and 1 operating modes

In “timer” function (C/T = ‘0’) the register is incremented every machine cycle. Therefore the count

rate is

OSC/12.

In “counter” function the register is incremented in response to a 1-to-0 transition at its

corresponding external input pin (P3.4/T0, P3.5/T1). Since it takes two machine cycles to detect a

falling edge the max. count rate is

OSC/24. External inputs INT0 and INT1 (P3.2, P3.3) can be

programmed to function as a gate to facilitate pulse width measurements. Figure 7 illustrates the

input clock logic.

Figure 7

Timer/Counter 0 and 1 Input Clock Logic

Mode Description

TMOD

Input Clock

Gate

C/T

internal

external (max)

8-bit timer/counter with a

divide-by-32 prescaler

OSC/12

× 32

OSC/24

× 32

16-bit timer/counter

OSC/12

OSC/24

8-bit timer/counter with

8-bit auto-reload

OSC/12

OSC/24

Timer/counter 0 used as one

8-bit timer/counter and one

8-bit timer

Timer 1 stops

OSC/12

OSC/24

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