Specifications

Counter/Timers (8254)
The counter status format is shown in Figure 11-5. Bits D5 through
D0 contain the counter’s programmed mode exactly as written in the
last Mode Control Word. OUTPUT via D7 contains the current state
of the OUT pin. This allows you to monitor the counter’s output via
software, possibly eliminating some hardware from a system.
D7 D6 D5 D4 D3 D2 D1 D0
Output
Null
Count
RW1 RW0 M2 M1 M0 BCD
I/O Address = 43h RD = 0
WR = 1
D7 1 = OUT Pin is 1
0 = OUT Pin is 0
D6 1 = Null Count
0 = Count available for reading
D5-D0 Counter programmed mode (see Figure 11-3)
Figure 11–5. Counter Status Format.
11-12