z86d73 ZiLOG Semiconductor, z86d73 Datasheet - Page 50

• Manufacturer Part Number: z86d73
• Description: 40/44/48-pin Low-voltage
• Manufacturer: ZiLOG Semiconductor

Negative Edge
SCLK
PS019402-1103
Positive Edge
CTR0 D4, D3
Z8 Data Bus
Z8 Data Bus
Select
Clock
Caution:
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.
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.
TC8H
HI8
Clock
Do not write these registers at the time the values are to be loaded into
the counter/timer to ensure known operation.
allowed (a non-function occurs).
from 0 to
P
Counter T8
FFh
R
8-Bit
to
E
FEh
L
.
I
M
TC8L
LO8
I
An initial count of 0 causes TC8 to count
N
A
40/44/48-Pin Low-Voltage IR OTP
CTR0 D2
R
Y
An initial count of 1 is not
CTR0 D1
T8_OUT
Z86D73
IRQ4
44