CHAPTER 4

DEVICE CONFIGURATION

The 8XC251Sx provides user design flexibility by configuring certain operating features at de- vice reset. These features fall into the following categories:

•external memory interface (page mode, address bits, pre-programmed wait states and the address range for RD#, WR#, and PSEN#)

•source mode/binary mode opcodes

•selection of bytes stored on the stack by an interrupt

•mapping of the upper portion of on-chip code memory to region 00:

You can specify a 16-bit, 17-bit, or 18-bit external address bus (256 Kbyte external address space). Wait state configurations provide pre-programmed 0, 1, 2, or 3 wait states.

This chapter provides a detailed discussion of 8XC251Sx device configuration. It describes the configuration bytes and provides information to aid you in selecting a suitable configuration for your application. It discusses the choices involved in configuring the external memory interface and shows how the internal memory maps into the external memory. See 4.5, “Configuring the External Memory Interface.” Section 4.6, “Opcode Configurations (SRC),” discusses the choice of source mode or binary mode opcode arrangements.

4.1CONFIGURATION OVERVIEW

The configuration of the MCS® 251 microcontroller is established by the reset routine based on information stored in configuration bytes. The 8XC251Sx microcontrollers store configuration information in two configuration bytes located in code memory. Devices with no on-chip code memory fetch configuration data from external memory. Factory programmed ROM devices use customer provided configuration data supplied on floppy disc.

4.2DEVICE CONFIGURATION

The 8XC251Sx reserves the top eight bytes of the memory address map (FF:FFF8H–FF:FFFFH) for an eight-byte configuration array (Figure 4-1). The two lowest bytes of the configuration array are assigned to the user configuration bytes UCONFIG0 (FF:FFF8H) and UCONFIG1 (FF:FFF9H). For ROM/OTPROM/EPROM devices, configuration information is stored in on- chip non-volatile memory at these addresses. For devices without on-chip ROM/OTPROM/EPROM, configuration information is accessed from external memory.

4-1

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Intel 8XC251SA, 8XC251SP, 8XC251SQ, 8XC251SB, Embedded Microcontroller manual Configuration Overview, Device Configuration
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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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