8254 Просмотр технического описания (PDF) - Intel

Номер в каталоге

Компоненты Описание

производитель

8254

PROGRAMMABLE INTERVAL TIMER

Intel 

8254

Figure 16 Mode 1

231164 – 8

initial count has expired OUT goes low for the re-

mainder of the count Mode 3 is periodic the se-

quence above is repeated indefinitely An initial

count of N results in a square wave with a period of

N CLK cycles

GATE e 1 enables counting GATE e 0 disables

counting If GATE goes low while OUT is low OUT is

set high immediately no CLK pulse is required A

trigger reloads the Counter with the initial count on

the next CLK pulse Thus the GATE input can be

used to synchronize the Counter

After writing a Control Word and initial count the

Counter will be loaded on the next CLK pulse This

allows the Counter to be synchronized by software

also

Writing a new count while counting does not affect

the current counting sequence If a trigger is re-

ceived after writing a new count but before the end

of the current half-cycle of the square wave the

Counter will be loaded with the new count on the

next CLK pulse and counting will continue from the

12

Share Link: