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4-11
MEMORY PARTITIONS
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
Address:
Reset State:
1FE0H
00H
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
0
EA_STAT
IRAM
—
—
—
—
—
—
Bit
Number
Bit
Mnemonic
Function
7
EA_STAT
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.)
6
IRAM
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
5:0
—
Reserved; always write as zeros.
Figure 4-3. Internal RAM Control (IRAM_CON) Register
Содержание 8XC196NT
Страница 1: ...8XC196NT Microcontroller User s Manual...
Страница 2: ...8XC196NT Microcontroller User s Manual June 1995 Order Number 272317 003...
Страница 22: ...1 Guide to This Manual...
Страница 23: ......
Страница 35: ......
Страница 36: ...2 Architectural Overview...
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Страница 50: ...3 Programming Considerations...
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Страница 66: ...4 Memory Partitions...
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Страница 104: ...5 Standard and PTS Interrupts...
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Страница 148: ...6 I O Ports...
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Страница 176: ...7 Serial I O SIO Port...
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Страница 194: ...8 Synchronous Serial I O SSIO Port...
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Страница 212: ...9 Slave Port...
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Страница 232: ...10 Event Processor Array EPA...
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Страница 270: ...11 Analog to digital Converter...
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Страница 292: ...12 Minimum Hardware Considerations...
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Страница 306: ...13 Special Operating Modes...
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Страница 318: ...14 Interfacing with External Memory...
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Страница 362: ...15 Programming the Nonvolatile Memory...
Страница 363: ......
Страница 408: ...A Instruction Set Reference...
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Страница 476: ...B Signal Descriptions...
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Страница 494: ...C Registers...
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Страница 566: ...Glossary...
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Страница 580: ...Index...
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