Intel Microcontroller, 80C196NU, 8XC196NP manual Remapping Internal ROM 83C196NP only

8XC196NP, 80C196NU USER’S MANUAL

5.4REMAPPING INTERNAL ROM (83C196NP ONLY)

The 83C196NP’s 4 Kbytes of ROM are located in FF2000–FF2FFFH. By using the REMAP bit (CCB1.2) and the EA# input, you can also access these locations in external memory (page 0FH or page 00H). The REMAP bit is loaded from CCB1 upon leaving reset and cannot be changed until the next reset. Tie EA# low to access external memory or tie it high to access the on-chip ROM. (Refer to the EA# description in Appendix B for additional information on using the EA# pin.)

NOTE

The EA# input is effective only for accesses to the 83C196NP’s on-chip ROM (FF2000–FF2FFFH). For an access to any other location, the value of EA# is irrelevant.

Without remapping (CCB1.2 = 0), an access to FF2000–FF2FFFH is directed to internal ROM (FF2000–FF2FFFH) if EA# is high and to external memory (F2000–F2FFFH) if EA# is low. In either case, data in this area must be accessed with extended instructions.

With remapping enabled (CCB1.2 = 1) and EA# high, you can access the contents of FF2000– FF2FFFH in two ways:

•in internal ROM (FF2000–FF2FFFH) using an extended instruction

•in external memory (002000–002FFFH) us ing a nonextended instruction. This makes the far data in FF2000–FF2FFFH acces sible as near data.

With remapping enabled (CCB1.2 = 1) and EA# low, you can access the contents of FF2000– FF2FFFH in external memory (F2000–F2FFFH) using an extended instruction.

An advantage of remapping ROM is that it makes the data in ROM accessible as near data in ex- ternal memory page 00H. The data can then be accessed more quickly with nonextended instruc- tions. An advantage of not remapping ROM is that the corresponding area in external memory page 00H is available for storing additional near data.

5-22