Z87100 Datasheet, PDF (18/48 Pages) Zilog, Inc. – Wireless Transmitter

Z87100
Wireless Transmitter
Zilog
FUNCTIONAL DESCRIPTION (Continued)
The 6-bit Prescaler divide the input frequency of the clock
source by any integer number from 1 to 64. Each prescaler
drives its counter, which decrements the value (1 to 256)
that has been loaded into the counter. When the counter
reaches the end of count, a timer interrupt request, IRQ4
(T0) or IRQ5 (T1), is generated.
The counters are programmed to start, stop, restart to con-
tinue, or restart from the initial value. The counters can
also be programmed to stop upon reaching zero (single-
pass mode) or to automatically reload the initial value and
continue counting (modulo-n continuous mode).
The counters, but not the Prescaler, may be read at any
time without disturbing their value or count mode. The
clock source for T1 is user-definable and can be either the
internal microprocessor clock divided by four, or an exter-
nal signal input through Port 3. The Timer Mode register
configures the external timer input (P31) as an external
clock, a trigger input that can be retriggerable or non-retrig-
gerable, or as a gate input for the internal clock. Port 3, line
P36 serves as a timer output (T_OUT) through which T0, T1
or the internal clock can be output. The counter/timers can
be cascaded by connecting the T0 output to the input of
T1.
Interrupts. The Z87100 has six different interrupts from
six different sources. The interrupts are maskable and pri-
oritized (Figure 15). The six sources are divided as follows;
two sources are claimed by Port 3 lines P31 and P33, two
sources in the counter/timers, one source for the PN mod-
ulator and one source for the time base generator. The In-
terrupt Mask Register globally or singularly enables or dis-
ables the six interrupt requests (Table 2).
IRQ0 IRQ2
IRQ1, 3, 4, 5
Interrupt
Edge
Select
IRQ (D6, D7)
IRQ
3-18
IMR
Interrupt
Request
Global
Interrupt
Enable
IPR
PRIORITY
LOGIC
Vector Select
Figure 15. Interrupt Block Diagram
PRELIMINARY
6
DS96WRL0700