PROGRAMMING CONSIDERATIONS

4.2.3.4Indirect Addressing with the Stack Pointer

You can also use indirect addressing to access the top of the stack by using the stack pointer as the WORD register in an indirect reference. The following instruction uses indirect addressing with the stack pointer:

PUSH [SP]

; duplicate top of stack

;SP ← SP +2

4.2.4Indexed Addressing

Indexed addressing calculates an address by adding an offset to a base address. There are three variations of indexed addressing: short-indexed, long-indexed, and zero-indexed. Both short- and long-indexed addressing are used to access a specific element within a structure. Short-indexed addressing can access up to 255 byte locations, long-indexed addressing can access up to 65,535 byte locations, and zero-indexed addressing can access a single location. An instruction can con- tain only one indexed reference; any remaining operands must be direct references.

4.2.4.1Short-indexed Addressing

In a short-indexed instruction, you specify the offset as an 8-bit constant and the base address as an indirect address register (a WORD). The following instructions use short-indexed addressing.

LD

AX,12H[BX]

;

AX

← MEM_WORD(BX+12H)

MULB

AX,BL,3[CX]

;

AX

← BL × MEM_BYTE(CX+3)

The instruction LD AX,12H[BX] loads AX with the contents of the memory location that resides at address BX+12H. That is, the instruction adds the constant 12 (the offset) to the contents of BX (the base address), then loads AX with the contents of the resulting address. For example, if BX contains 1000H, then AX is loaded with the contents of location 1012H. Short-indexed address- ing is typically used to access elements in a structure, where BX contains the base address of the structure and the constant (12H in this example) is the offset of a specific element in a structure.

You can also use the stack pointer in a short-indexed instruction to access a particular location within the stack, as shown in the following instruction.

LD AX,2[SP]

4.2.4.2Long-indexed Addressing

In a long-indexed instruction, you specify the base address as a 16-bit variable and the offset as an indirect address register (a WORD). The following instructions use long-indexed addressing.

LD

AX,TABLE[BX]

;

AX

←

MEM_WORD(TABLE+BX)

AND

AX,BX,TABLE[CX]

;

AX

←

BX AND MEM_WORD(TABLE+CX)

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Intel 80C196NU, 8XC196NP manual Indexed Addressing, Indirect Addressing with the Stack Pointer, Short-indexed Addressing
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Microcontroller, 80C196NU, 8XC196NP specifications

The Intel 8XC196NP and 80C196NU microcontrollers are part of Intel's renowned 16-bit microcontroller series that gained popularity in the 1980s and 1990s for embedded systems applications. Designed for a variety of applications, these microcontrollers are characterized by their robust performance, versatility, and industry-standard architecture.

The 8XC196NP features an enhanced instruction set with over 100 instructions, allowing for efficient code execution. It operates at clock speeds up to 16 MHz, which contributes to improved performance in time-sensitive applications. The microcontroller is equipped with a 16-bit data bus, enabling more efficient data handling compared to its 8-bit predecessors, thus accommodating complex algorithms and large data sets.

In terms of memory architecture, the 8XC196NP supports an addressable memory space of up to 64 KB of program memory and 64 KB of data memory. This configuration provides sufficient space for large applications while ensuring fast data access. The microcontroller includes integrated features such as timers, serial I/O capabilities, and interrupt processing, which enhance its functionality for real-time applications and control mechanisms.

The 80C196NU, on the other hand, is designed for lower power operation, making it suitable for battery-powered devices. This microcontroller maintains similar features to the 8XC196NP while offering advancements that support low-power consumption. The 80C196NU can also function in a range of temperature environments, making it adaptable for industrial applications.

Both the 8XC196NP and 80C196NU support external memory interfacing, allowing designers to expand the system's capability by connecting additional ROM and RAM. This flexibility makes them appealing for developing complex systems, such as motor controls, industrial automation, and consumer electronics.

Another standout feature of these microcontrollers is their built-in debugging capabilities. Intel provided hardware and software tools that enabled developers to test and troubleshoot their applications effectively, reducing the development time and increasing reliability.

Overall, the Intel 8XC196NP and 80C196NU microcontrollers stand out for their dependability, versatility, and performance, contributing significantly to the evolution of embedded system design. Their legacy continues to influence modern microcontroller technology, ensuring their relevance in a wide array of applications today.
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