Z86L02 datasheet(22/37 Pages) ZILOG

22 / 37 page

Z86C02/E02/L02

Cost Effective, 512-Byte ROM CMOS Z8® Microcontrollers

Zilog

P R E L I M I N A R Y

DS96DZ80301

FUNCTIONAL DESCRIPTION (Continued)

Interrupts. The Z8 has five interrupts from four different

sources. These interrupts are maskable and prioritized

(Figure 16). The sources are divided as follows: the falling

edge of P31 (AN1), P32 (AN2), P33 (REF), the rising edge

of P32 (AN2), and one counter/timer. The Interrupt Mask

five interrupt requests (Table 5).

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 Z8 interrupts 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 in-

terrupt. This memory location and the next byte contain the

16-bit starting address of the interrupt service routine for

that particular interrupt request.

To accommodate polled interrupt systems, interrupt inputs

are masked and the interrupt request register is polled to

determine which of the interrupt requests needs service.

User must select any Z86E08 mode in Zilog's C12 ICE-

BOX™ emulator. The rising edge interrupt is not directly

supported on the Z86CCP00ZEM emulator.

Figure 15. Counter/Timers Block Diagram

OSC

÷ 2

6-Bit

Down

Counter

8-Bit

Down

Counter

PRE1

Initial Value

Current Value

Clock

Logic

IRQ5

Internal Data Bus

Write

Read

Internal Clock

Gated Clock

Triggered Clock

P31

External Clock

Internal

Clock

÷4

Table 5. Interrupt Types, Sources, and Vectors

Vector

Name

Source

Location

Comments

IRQ0

AN2(P32)

0,1

External (F)Edge

IRQ1

REF(P33)

2,3

External (F)Edge

IRQ2

AN1(P31)

4,5

External (F)Edge

IRQ3

AN2(P32)

6,7

External (R)Edge

IRQ4

Reserved

8,9

Reserved

IRQ5

10,11

Internal

Notes:

F = Falling edge triggered

R = Rising edge triggered

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