L8708H datasheet(26/66 Pages) ZILOG

26 / 66 page

Z86L88/81/86/87/89/73

IR/Low-Voltage Microcontroller

P R E L I M I N A R Y

DS96LV00800

FUNCTIONAL DESCRIPTION

The Z86LXX family of IR CCP incorporates special func-

tions to enhance the Z8's functionality in consumer and

battery operated applications.

Program

Memory.

The

Z86LXX

family

addresses

16/24/32 Kbytes of internal program memory. The first

twelve bytes are reserved for interrupt vectors. These lo-

cations contain the five 16-bit vectors which correspond to

the five available interrupts. In all cases, at addresses 32K

and greater, external program memory fetches will be ex-

ecuted (provided proper A/D port mode register settings).

Refer to external memory timing specifications. In Rom-

less mode, program memory fetches begin at address

000Ch and data memory fetches begin at address 0000h.

RAM. The Z86LXX devices all have 256 bytes of RAM

which make up the Register file.

External Memory (/DM). The Z86LXX addresses up to 32

Kbytes of external memory beginning at address 32768

(Figure 20). External data memory is included with, or sep-

arated from, the external program memory space. /DM, an

optional I/O function that is programmed to appear on P34,

is used to distinguish between data and program memory

space. The state of the /DM signal is controlled by the type

of instruction being executed. An LDC opcode references

PROGRAM (/DM inactive) memory, and an LDE instruc-

tion references data (/DM active Low) memory.

Figure 19. Program Memory Map(32K ROM)

External ROM

Location of

First Byte of

Instruction

Executed

After RESET

Interrupt

Vector

(Lower Byte)

Interrupt

Vector

(Upper Byte)

Reserved

IRQ4

IRQ3

IRQ2

IRQ1

IRQ0

Reserved

On-Chip

ROM

32768

Reset Start Address

Figure 20. External Memory Map

65535

External

Data

Memory

Not Addressable

32,768

L8708H Datasheet(PDF) 26 Page - Zilog, Inc.

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