Internal Ram (Code Ram) - Intel 8XC196NT User Manual

4.2.4

Internal RAM (Code RAM)

The 8XC196NT has 512 bytes of internal code RAM in locations 0400–05FFH. This memory
can be accessed from either page 00H or page FFH. Although it is called code RAM to distinguish
it from register RAM, this internal RAM can store either code or data. The code RAM is accessed
through the memory controller, so code executes as it would from external memory with zero wait
states. Data stored in this area must be accessed with indirect or indexed addressing, so data ac-
cesses to this area take longer than data accesses to the register RAM. The code RAM cannot be
windowed.
During application development, you may need to use external memory to store code and data
that will later reside in the internal code RAM. The IRAM_CON register (Figure 4-3) provides a
simple method for handling this situation.
IRAM_CON
The internal RAM control (IRAM_CON) register has two functions related to memory accesses. The
IRAM bit allows you to control access to locations 0400–05FFH. The EA_STAT bit allows you to
determine the status of the EA# pin, which controls access to locations FF2000–FF9FFFH.
7
EA_STAT IRAM
Bit Bit
Number Mnemonic
7 EA_STAT
6 IRAM
5:0 —
Figure 4-3. Internal RAM Control (IRAM_CON) Register
— —
EA# Status:
This read-only bit contains the complement of the EA# pin, which
controls whether accesses to locations FF2000–FF9FFFH are directed
to the internal OTPROM or to external memory.
1 = the EA# pin is active (accesses are directed to external memory)
0 = the EA# pin in inactive (accesses are directed to the OTPROM)
("Remapping Internal OTPROM (87C196NT Only)" on page 4-23
describes additional options for OTPROM access.)
Internal RAM Control:
This bit controls whether accesses to locations 0400–05FFH are
directed to internal code RAM or to external memory.
1 = use external memory
0 = use the internal code RAM
Reserved; always write as zeros.
MEMORY PARTITIONS
Address:
Reset State:
— —
Function
1FE0H
00H
0
— —
4-11