Z86K14 datasheet(16/24 Pages) ZILOG

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Z86K13/K14/K15/K16/K17/K18

CMOS Z8® 8-Bit MCU Keyboard Controllers

Zilog

P R E L I M I N A R Y

DS97KEY0204

PIN FUNCTIONS (Continued)

Interrupts. The Z86K15 has five different interrupts from

five different sources. These interrupts are maskable and

prioritized (Figure 16). The five sources are divided as fol-

lows: four sources are claimed by Port 3 lines P33-P30,

and the other is claimed by the counter/timer. The Interrupt

Masked Register globally or individually enables or dis-

ables the five interrupts requests.

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 interrupts are

vectored through locations in the program memory. When

an interrupt machine cycle is activated an interrupt request

is granted. Thus, this disables all of the subsequent inter-

rupts, saves the Program Counter and status flags, and

then branches to the program memory vector location re-

served for that interrupt. This memory location and the

next byte contain the 16-bit 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 request needs service.

RC Oscillator. The Z86K13/14/15 provides an internal ca-

pacitor to accommodate an RC oscillator configuration. A

1% precision resistor is necessary to achieve

±10% accu-

rate frequency oscillation.

The Z86K15 also accepts external clock from (RCIN) with

(AGND) connected to V

CC (Figure 17).

Figure 16. Interrupt Block Diagram

IRQ

IMR

Priority

Logic

Global

Interrupt

Enable

Vector Select

Interrupt

Request

IRQ0-IRQ4

IPR

Figure 17. RC Oscillator Configuration

RCIN

Precision

CLKOUT

VCC

RC Oscillator

External Clock

RCIN

AGND

VCC

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