Mode 5 – Retriggering The Strobe; Mode 5 – Writing A New Count Value - Intel 386 User Manual

Figure 10-20 shows retriggering the strobe with a gate-trigger. On the CLKINn pulse following
the retrigger, the counter reloads the count. The control logic then decrements the count on each
succeeding CLKINn pulse. OUTn remains high until the count reaches zero, then strobes low for
one CLKINn pulse.
Control
Word = 1AH
Writes to
n
Counter
n
CLKIN
n
GATE
n
OUT
Count ? ?
Figure 10-21 shows the writing of a new count value. The counter waits for a gate-trigger to load
the new count; it does not affect the current sequence until the counter receives a trigger. On the
CLKINn pulse following the trigger, the control logic loads the new count. The control logic then
decrements the count on each succeeding CLKINn pulse. OUTn remains high until the count
reaches zero, then strobes low for one CLKINn pulse.
Control
Word = 1AH
Writes to
n
Counter
n
CLKIN
V
CC
n
GATE
n
OUT
?
Count
Figure 10-21. Mode 5 – Writing a New Count Value
Count = 3
? ? ? ? 0003 0002 0003 0002 0001 0000
Figure 10-20. Mode 5 – Retriggering the Strobe
Count = 3 Count = 5
? ? ? ? 0003 0002 0001 0000 FFFF FFFE 0005
TIMER/COUNTER UNIT
FFFF FFFE
A2404-01
0004 0003
A2405-01
10-19