Z86318 Datasheet, PDF (19/26 Pages) Zilog, Inc. – Z8 MCU 8-BIT MICROCONTROLLER

Z86318
Z8^® MCU 8-Bit Microcontroller
Interrupts. The Z86318 features four interrupts from four To accommodate polled interrupt systems, interrupt inputs
different sources. These interrupts are maskable and pri- are masked and the Interrupt Request Register is polled to
oritized (Figure 16). The four sources are divided as fol- determine which of the interrupt requests needs service.
lows: the falling edge of P31, P33, and the two counter/tim-
1
ers. The Interrupt Mask Register globally or individually
Table 3. Interrupt Types, Sources, and Vectors
enables or disables the four interrupt requests (Table 4).
Source Name
Vector Location Comments
When more than one interrupt is pending, priorities are re-
solved by a programmable priority encoder that is con-
trolled by the Interrupt Priority register. All Z86318 inter-
rupts are vectored through locations in program memory.
When an interrupt machine cycle is activated, an interrupt
request is granted. This disables all subsequent interrupts,
saves the Program Counter and Status Flags, and then
branches to the program memory vector location reserved
for that interrupt. This memory location and the next byte
contain the 16-bit starting address of the Interrupt Service
Routine for that particular interrupt request.
P33
IRQ1
2,3
P31
IRQ2
4,5
T0
IRQ4
8,9
T1
IRQ5
10,11
Notes:
F = Falling edge triggered
R = Rising edge triggered
External
External
Internal
Internal
(F)Edge
(F)Edge
IRQ0 - IRQ5
IRQ
IMR
6
Interrupt
Request
Global
Interrupt
Enable
IPR
Priority
Logic
Vector Select
Figure 16. Interrupt Block Diagram
Clock. The Z86318 on-chip oscillator has a parallel-reso-
nant amplifier for connection to a crystal, ceramic resona-
tor, or any suitable external clock source (XTAL1 = Input,
XTAL2 = Output). The crystal should be AT cut, 4 MHz
max, with a series resistance (RS) less than or equal to
100 Ohms.
The crystal should be connected across XTAL1 and
XTAL2 using the recommended capacitors (capacitance is
between 10 pF to 250 pF and is specified by the crystal
manufacturer, ceramic resonator and PCB layout) from
each pin to ground (see Figure 17).
PRELIMINARY
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