Specifications

Counter/Timers (8254)
COUNTER/TIMER ARCHITECTURE
Each counter is fully independent and may operate in a unique mode.
Only one counter/timer is described since the three counters are
identical in operation. Figure 11-2 shows the internal block diagram
of the counter/timer. Although the Control Word register is not a part
of the counter/timer itself, its contents determine how the counter
operates and it is therefore illustrated in the figure.
STATUS
LATCH
CONTROL
WORD
REGISTER
STATUS
REGISTER
CONTROL
LOGIC
CR
M
CR
L
CE
OL
M
OL
L
CLKn
GATEn
OUTn
INTERNAL BUS
Figure 11–2. Internal Block Diagram of a Counter.
11-4