Intel 8XC196NP Benutzerhandbuch

5-24

For nonextended instructions, the EP_REG register provides the page number. Data and constants
in this page are called near data and near constants. 

The 8XC196NP allows you to change the value of EP_REG to control which 
memory page a nonextended instruction accesses. However, software tools 
require that EP_REG be equal to 00H. The 80C196NU forces all nonextended 
data accesses to page 00H. You cannot use EP_REG to change pages.

Data outside the page specified by EP_REG is called far data. To access far data, you must use
extended instructions. For extended instructions, the CPU provides the page number.

The code example below illustrates the use of extended instructions to access data in page 01H.

EP_REG

EQU 1FE5H
RSEG AT 1CH

TEMP:

DSW 1

RESULT:

DSW 1
CSEG AT 0FF2080H
.

;some code

.

;

.

;

SUBB:

PUSHA

;save flags, disable interrupts

LD

TEMP,#1234H

;

EST

TEMP,010600H

;store temp value in 010600H

ADD

RESULT,TEMP,#4000H

;do something with registers

EST

RESULT,010602H

;store result in 010602H

.

;more eld/est instructions

.

;

.

;

POPA

;restore flags and interrupts

RET

;

.

;more code

.

;

.

;

DONE:

BR DONE
END

A2514-01

From CPU

16-bit Data Address Register

23

16 15

0

From EP_REG

16-bit Data Address Register

23

16 15

0

Nonextended Address

Extended Address