8XC251SA, SB, SP, SQ USER’S MANUAL

It is convenient to view the unsegmented, 16-Mbyte memory space as consisting of 256 64-Kbyte regions, numbered 00: to FF:.

NOTE

The memory space in the MCS 251 architecture is unsegmented. The 64- Kbyte “regions” 00:, 01:, ..., FF: are introduced only as a convenience for discussions. Addressing in the MCS 251 architecture is linear; there are no segment registers.

MCS 251 microcontrollers can have up to 64 Kbytes of on-chip code memory in region FF:. On- chip data RAM begins at location 00:0000H. The first 32 bytes (00:0000H–00:001FH) provide storage for a part of the register file. On-chip, general-purpose data RAM begins at 00:0020H. The sizes of the on-chip code memory and on-chip RAM depend on the particular device.

The register file has its own address space (Figure 3-1). The 64 locations in the register file are numbered decimally from 0 to 63. Locations 0–7 represent one of four switchable register banks, each having 8 registers. The 32 bytes required for these banks occupy locations 00:0000H– 00:001FH in the memory space. Register file locations 8–63 do not appear in the memory space. See “8XC251SA, SB, SP, SQ Register File” on page 3-10 for a further description of the register file.

The SFR space can accommodate up to 512 8-bit special function registers with addresses S:000H–S:1FFH. Some of these locations may be unimplemented in a particular device. In the MCS 251 architecture, the prefix “S:” is used with SFR addresses to distinguish them from the memory space addresses 00:0000H–00:01FFH. See “Special Function Registers (SFRs)” on page 3-16 for details on the SFR space.

3.1.1Compatibility with the MCS® 51 Architecture

The address spaces in the MCS 51 architecture† are mapped into the address spaces in the MCS 251 architecture. This mapping allows code written for MCS 51 microcontrollers to run on MCS 251 microcontrollers. (Chapter 5, “Programming,” discusses the compatibility of the two instruc- tion sets.)

Figure 3-2 shows the address spaces for the MCS 51 architecture. Internal data memory locations 00H–7FH can be addressed directly and indirectly. Internal data locations 80H–FFH can only be addressed indirectly. Directly addressing these locations accesses the SFRs. The 64-Kbyte code memory has a separate memory space. Data in the code memory can be accessed only with the MOVC instruction. Similarly, the 64-Kbyte external data memory can be accessed only with the MOVX instruction.

† MCS®51 Microcontroller Family User’s Manual

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Intel Embedded Microcontroller, 8XC251SA, 8XC251SP, 8XC251SQ, 8XC251SB manual Compatibility with the MCS 51 Architecture
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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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