Z86D73 Datasheet, PDF (50/92 Pages) Zilog, Inc. – 40/44/48-Pin Low-Voltage IR OTP

Z86D73
40/44/48-Pin Low-Voltage IR OTP
44
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, and sets the timeout sta-
tus bit (CTR0, D5), thereby generating 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 21.
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 21. 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 initial count of 1 is not
allowed (a non-function occurs). An initial count of 0 causes TC8 to count
from 0 to FFh to FEh.
PS019402-1103
PRELIMINARY