CX51: CODE VS ECODE

Information in this article applies to:

• CX51 All Versions

QUESTION

Why does my build (on a Philips MX device) show ECODE beginning at 0x000000?

ANSWER

Keep in mind that CODE and ROM are not the same thing.

CODE is the location of executable instructions in the traditional 8051ROM space. It uses 16-bit addressing, and can have a maximum size of 64k.

ECODE is the extended code space, available on "super 8051s" such as the Philips MX. It uses 24-bit addressing, and can have a maximum size of 8meg.

ECODE can overlap CODE, but since there's an additional byte of address information to set, 24-bit access is slower.

CONST and NCONST are equivalent to CODE and ECODE respectively, and are used to store constant data in ROM. They have the same restrictions as to size and speed as their counterparts.

MORE INFORMATION

• Refer to CLASSES in the LX51 User's Guide.

SEE ALSO

• CX51: LOCATING CODE IN PHILIPS MX INTERNAL CODE MEMORY
• AX51: LOCATING AN ECODE SEGMENT AT A FIXED ADDRESS
• Application Note 160: Programming the Philips 51MX Architecture with the Keil PK51

Last Reviewed: Friday, January 12, 2007