Z86L81 Datasheet, PDF (45/88 Pages) Maxim Integrated Products – 28-Pin Low-Voltage Infrared Microcontrollers

Z86L81/86/98
28-Pin Low-Voltage Infrared Microcontrollers
39
When T8 is enabled, the output T8_OUT switches to the initial value (CTR1, D1).
If the initial value (CTR1, D1) is 0, TC8L is loaded; otherwise, TC8H is loaded into
the counter. In Single-Pass Mode (CTR0, D6), T8 counts down to 0 and stops,
T8_OUT toggles, the timeout status bit (CTR0, D5) is set, and a timeout interrupt
can be generated if it is enabled (CTR0, D1). In Modulo-N Mode, upon reaching
terminal count, T8_OUT is toggled, but no interrupt is generated. From that point,
T8 loads a new count (if the T8_OUT level now is 0), TC8L is loaded; if it is 1,
TC8H is loaded. T8 counts down to 0, toggles T8_OUT, sets the timeout status bit
(CTR0, D5) and generates an interrupt if enabled (CTR0, D1). One cycle is thus
completed. T8 then loads from TC8H or TC8L according to the T8_OUT level, and
repeats the cycle. See Figure 16.
Z8 Data Bus
CTR0 D2
Positive Edge
Negative Edge
IRQ4
HI8
LO8
CTR0 D4, D3
CTR0 D1
SCLK
Clock
Select
Clock
8-Bit
Counter T8
T8_OUT
Z8 Data Bus
TC8H
TC8L
Figure 16. 8-Bit Counter/Timer Circuits
You can modify the values in TC8H or TC8L at any time. The new values take
effect when they are loaded.
Caution: Do not write these registers at the time the values are to be
loaded into the counter/timer to ensure known operation. An
19-4615; Rev 0; 4/09