Advantech PCI-1751U Instrukcja Użytkownika Pobierz pdf (Strona 23)

19 Chapter 3

3.3 Timer/Counter Operation

3.3.1 Introduction

The PCI-1751U includes one 8254 compatible programmable timer/

counter chip which provides three 16-bit counters, designated as Timer 0,

Timer1 and Counter 2. Each has 6 operation modes. Timer 0 and Timer

1 can be used separately or can be cascaded to create one 32-bit timer.

Both Timer 1 and Counter 2 can generate interrupts to the computer.

Please refer to Appendix A for more information on the operation modes

of the counter chip. The block diagram of the timer/counter system is

shown in Figure 3-2.

Figure 3.2: Timer and counter structure

3.3.2 Timer 0 & 1: Two 16-bit Timers or One 32-bit Timer

Timer 0 and Timer 1 of the counter chip can be used separately or can be

cascaded to create a 32-bit programmable timer by setting jumper JP2.

By setting the clock source of Timer 1 to be an external source, you can

user Timer 0 and Timer 1 as two separate 16-bit timers. By setting the

clock source of Timer 1 to be the output of Timer 0 (internal source) these

two timers are cascaded to become one 32-bit timer.

1 2 ... 18 19 20 21 22 23 24 25 26 27 28 ... 37 38

Brak uwag

Advantech PCI-1751U Instrukcja Użytkownika Strona 23