8051 XDATA IDATA DATA FX2

FX2 데이타시트

http://www.esacademy.co.kr/read/8051pro/8051pro_03.htm

Segment Naming Conventions

Segment Prefix Memory Type Description

?PR? program         Executable program code

?CO? code Constant data in program memory

?BI?         bit         Bit data in internal data memory

?BA? bdata Bit-addressable data in internal data memory

?DT?         data         Internal data memory

?FD?         far         Far memory (RAM space)

?FC? const far         Far memory (constant ROM space)

?ID?         idata         Indirectly-addressable internal data memory

?PD? pdata Paged data in external data memory

?XD? xdata Xdata memory (RAM space)

?XC? const xdata Xdata memory (constant ROM space)

keil 유저가이드

data 128 Bytes directly addressable on-chip RAM.
idata 256 Bytes indirectly addressable on-chip RAM.
pdata 256 Bytes external RAM.
xdata 64KB extended RAM space.
code 64KB program memory.
bdata 16 Bytes bit-addressable RAM; mixed bit/byte access.

> The data area is the smallest, but most efficiently accessed area.
> Idata is the next most efficient. Xdata is by far the largest. To help
> keep the code small place the most frequently used data into data or
> idata. Use functions instead of duplicated code. Using bit types can
> help keep the code small. Use qualified pointers rather than generic
> pointers.
>
> Many of these suggestions make the code less portable and harder to
> support. My recommendation is to not use them until you need to, and
> then restrict it to isolated areas of code.

http://www.motherboardpoint.com/xdata-idata-data-differences-t169429.html

KEIL

Macro Assembler and Utilities

CODE, DATA, IDATA, XDATA

The BIT, CODE, DATA, IDATA, and XDATA directives assigns an address

value to the specified symbol. Symbols defined with the BIT, CODE, DATA,

IDATA, and XDATA directives may not be changed or redefined. The format

of theses directives is: