8051 internal RAM map — general-purpose storage region Is the statement true or false? “The last 96 locations in the internal data memory are reserved for general-purpose data storage and stack.”

Difficulty: Easy

Correct Answer: False

Explanation:


Introduction / Context:
Understanding the internal RAM layout of the 8051 is vital for stack placement, register bank usage, and bit-addressable operations. The lower 128 bytes are divided into specific regions, not all of which are general-purpose.


Given Data / Assumptions:

  • Classic 8051 lower internal RAM is 128 bytes (00h–7Fh).
  • Upper 128 bytes (80h–FFh) are SFRs in the original 8051.
  • General-purpose RAM and the stack usually occupy a subset of 00h–7Fh.


Concept / Approach:
Lower RAM map: 00h–1Fh = register banks (32 bytes), 20h–2Fh = bit-addressable area (16 bytes), 30h–7Fh = general-purpose RAM (80 bytes). The stack typically grows within this GPR area unless relocated by the programmer. Therefore, the “last 96 locations” claim is incorrect; it is actually 80 bytes (30h–7Fh).


Step-by-Step Solution:

1) Compute GPR size: 0x7F − 0x30 + 1 = 0x50 = 80 bytes.2) Recognize stack resides in GPR region by default (SP starts at 07h).3) Conclude the statement claiming 96 bytes is false.


Verification / Alternative check:
Refer to any 8051 memory map diagram showing the partitions of lower RAM and SFR space.


Why Other Options Are Wrong:

  • True: contradicts the canonical 80-byte size of the GPR region in classic 8051.


Common Pitfalls:
Confusing lower RAM size (128 bytes) with the GPR subset; miscounting the bit-addressable area as general-purpose.


Final Answer:
False

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