Table of Contents
Advertisement
Instruction fetches from FF2000–FF9FFFH are controlled by the EA# input:
•
If EA# is low, code executes from external memory (page 0FH).
•
If EA# is high, code executes from internal OTPROM (page FFH).
4.5.5
Data Fetches in the 1-Mbyte and 64-Kbyte Modes
Data fetches are the same in the 1-Mbyte and 64-Kbyte modes. The device can access data in any
page. Data accesses to page 00H are nonextended. Data accesses to any other page are extended.
This information on data fetches applies only for EP_REG = 00H.
Nonextended instructions can access the register file and peripheral SFRs from any page. Extend-
ed load and store instructions can access these locations from page 00H only; an extended load
or store instruction executing from any other page accesses external memory. For example, if
code is executing from page 05H, the following instructions write to different memory locations:
stb temp, 30H
estb temp, 30H
Memory-mapped SFRs can be accessed from page 00H only.
80C196NT:
Data accesses to the register file (0000–03FFH) and the SFRs (1F00–1FFFH) are directed to the
internal registers. All other data accesses are directed to external memory.
87C196NT:
Data accesses to the register file (0000–03FFH) and the SFRs (1F00–1FFFH) are directed to the
internal registers. Accesses to other locations are directed to external memory, except as noted
below:
Data accesses to FF2000–FF9FFFH depend on the EA# input:
•
If EA# is low, accesses are to external memory (page 0FH).
•
If EA is high, accesses are to the internal OTPROM (page FFH).
NOTE
;writes to address 30H in the register file
;writes to address 050030H in external memory
MEMORY PARTITIONS
4-27
Advertisement
Table of Contents
