PROGRAMMING

Table 5-4. Addressing Modes for Data Instructions in the MCS® 251 Architecture

 

 

 

 

Mode

Address Range of

Assembly Language

Comments

Operand

Notation

 

 

 

 

 

 

 

00:0000H– 00:001FH

R0– R15, WR0– WR30,

R0– R7, WR0–WR6, DR0, and

 

DR2 are in the register bank

Register

(R0–R7, WR0–WR3,

DR0– DR28, DR56, DR60

currently selected by the

 

 

DR0, DR2) (1)

 

PSW and PSW1.

 

 

 

 

 

 

 

Immediate,

N.A. (Operand is in the

#short = 1, 2, or 4

Used only in increment and

2 bits

instruction)

decrement instructions.

 

 

 

 

 

Immediate,

N.A. (Operand is in the

#data8 = #00H–#FFH

 

8 bits

instruction)

 

 

 

 

 

 

 

Immediate,

N.A. (Operand is in the

#data16 = #0000H– #FFFFH

 

16 bits

instruction)

 

 

 

 

 

 

 

Direct,

00:0000H–00:007FH

dir8 = 00:0000H–00:007FH

On-chip RAM

 

 

 

 

dir8 = S:080H– S:1FFH (2)

 

8 address bits

SFRs

SFR address

 

or SFR mnemonic

 

 

 

 

 

 

 

Direct,

00:0000H–00:FFFFH

dir16 = 00:0000H–00:FFFFH

 

16 address bits

 

 

 

 

 

 

 

 

Indirect,

00:0000H–00:FFFFH

@WR0–@WR30

 

16 address bits

 

 

 

 

 

 

 

 

Indirect,

00:0000H–FF:FFFFH

@DR0–@DR30, @DR56,

Upper 8 bits of DRk must be

24 address bits

@DR60

00H.

 

 

 

 

 

Displacement,

 

@WRj + dis16 =

Offset is signed; address

00:0000H–00:FFFFH

@WR0 + 0H through

16 address bits

wraps around in region 00:.

 

@WR30 + FFFFH

 

 

 

 

 

 

 

 

 

@DRk + dis24 =

 

Displacement,

00:0000H–FF:FFFFH

@DR0 + 0H through

Offset is signed, upper 8 bits

@DR28 + FFFFH,

24 address bits

of DRk must be 00H.

 

@DR56 + (0H–FFFFH),

 

 

 

 

 

@DR60 + (0H–FFFFH)

 

 

 

 

 

NOTES:

 

 

 

1.These registers are accessible in the memory space as well as in the register file (see section 3.3, “8XC251SA, SB, SP, SQ Register File.”

2.The MCS 251 architecture supports SFRs in locations S:000H–S:1FFH; however, in the 8XC251Sx, all SFRs are in the range S:080H–S:0FFH.

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Intel Embedded Microcontroller, 8XC251SA, 8XC251SP, 8XC251SQ, 8XC251SB manual @WR30 + Ffffh
Page 88 Page 90

Embedded Microcontroller, 8XC251SP, 8XC251SA, 8XC251SQ, 8XC251SB specifications

The Intel 8XC251 series of embedded microcontrollers is a family of versatile and powerful devices, designed to meet the demands of a wide range of applications. With models such as the 8XC251SB, 8XC251SQ, 8XC251SA, and 8XC251SP, this series offers unique features while maintaining a high level of performance and reliability.

At the heart of the 8XC251 microcontrollers is the 8051 architecture, which provides a 16-bit processor capable of executing complex instructions efficiently. This architecture not only allows for a rich instruction set but also facilitates programming in assembly language and higher-level languages like C, which are essential for developing sophisticated embedded systems.

One of the significant features of the 8XC251 family is its integrated peripherals, including timer/counters, serial communication interfaces, and interrupt systems. These peripherals enable developers to implement timing functions, data communication, and real-time processing, all of which are crucial in modern embedded applications. The 8XC251SB and 8XC251SQ models, for instance, come equipped with multiple I/O ports that allow for interfacing with other devices and systems, enhancing their functionality in various environments.

The memory architecture of the 8XC251 devices is noteworthy, featuring on-chip ROM, RAM, and EEPROM. The on-chip memory allows for fast access times, which is essential for executing programs efficiently. Moreover, the EEPROM serves as non-volatile memory, enabling the storage of configuration settings and important data that must be retained even when power is lost.

In terms of operating voltage, the 8XC251 devices are designed to operate in a wide range, typically between 4.0V and 6.0V. This flexibility makes them suitable for battery-powered applications, where energy efficiency is critical. The power management features, including reduced power modes, further enhance their suitability for portable devices.

Lastly, the 8XC251 series is supported by a wide range of development tools and resources, allowing engineers and developers to streamline the development process. This support, combined with the microcontrollers' robust features, makes the Intel 8XC251 family a reliable choice for various embedded applications, such as industrial automation, automotive systems, and consumer electronics.

Overall, the Intel 8XC251SB, 8XC251SQ, 8XC251SA, and 8XC251SP deliver high performance, versatility, and ease of use, making them a preferred choice for embedded system designers looking to develop efficient and effective solutions.
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