Intel 8XC196NT, User Manual

Page: 90 / 597

4-23
MEMORY PARTITIONS
4.4 REMAPPING INTERNAL OTPROM (87C196NT ONLY)
The 87C196NT’s 32 Kbytes of OTPROM are located in FF2000–FF9FFFH. By using the
REMAP bit (CCB2.2) and the EA# input, you can also access these locations in internal memory
page 00H or in external memory page 0FH (Table 4-13). The REMAP bit is loaded from the CCB
and the value of EA# is latched upon leaving reset; neither can be changed until the next reset.
You can read IRAM_CON.7 to determine the state of the EA# pin (bit 7 contains the complement
of EA#) and read CCR2.2 to determine the state of the REMAP bit.
NOTE
The EA# input is effective only for accesses to the internal OTPROM
(FF2000–FF9FFFH). For accesses to any other location, the value of EA# is
irrelevant. The REMAP bit is effective only when EA# is inactive. When EA#
is active, execution is external and the REMAP bit is ignored.
Without remapping (CCB2.2 = 0), an access to FF2000–FF2FFFH is directed to internal
OTPROM (FF2000–FF9FFFH) when EA# is high and to external memory (F2000–F9FFFH)
when EA# is low. In either case, data in this area must be accessed with extended instructions.
With remapping enabled (CCB2.2 = 1) and EA# inactive, you can access the contents of FF2000–
FF9FFFH in two ways:
•
in internal OTPROM (FF2000–FF9FFFH) using an extended instruction
•
in internal OTPROM (002000–009FFFH) using a nonextended instruction. This makes the
far data in FF2000–FF9FFFH accessible as near data.
With EA# active, the REMAP bit is ignored. You can access the contents of FF2000–FF9FFFH
in external memory (F2000–F9FFFH) using an extended instruction.
An advantage of remapping OTPROM is that it makes the data in OTPROM accessible as near
data in internal memory page 00H. The data can then be accessed more quickly with nonextended
instructions. An advantage of not remapping OTPROM is that the corresponding area in memory
page 00H is available for storing additional near data.
Table 4-13. Memory Access for the 87C196NT
REMAP
(CCB2.2)
EA# Instruction Type Memory Location Accessed
X asserted extended external memory, F2000–F9FFFH
0 deasserted extended internal OTPROM, FF2000–FF9FFFH
1 deasserted
extended internal OTPROM, FF2000–FF9FFFH
nonextended internal OTPROM, 002000–002FFFH