8XC251SA, SB, SP, SQ USER’S MANUAL

13.2.2 Nonpage Mode Bus Cycles

In nonpage mode, the external bus structure is the same as for MCS 51 microcontrollers. The up- per address bits (A15:8) are on port 2, and the lower address bits (A7:0) are multiplexed with the data (D7:0) on port 0. External code read bus cycles execute in approximately two state times. See Table 13-2 and Figure 13-2. External data read bus cycles (Figure 13-3) and external write bus cycles (Figure 13-4) execute in approximately three state times. For the write cycle (Figure 13-4), a third state is appended to provide recovery time for the bus. Note that the write signal WR# is asserted for all memory regions, except for the case of RD1:0 = 11, where WR# is assert- ed for regions 00:–01: but not for regions FE:–FF:.

State 1

State 2

XTAL

ALE

RD#/PSEN#

P0

A7:0

D7:0

A17/A16/P2

A17/A16/A15:8

A2807-04

Figure 13-2. External Code Fetch (Nonpage Mode)

State 1

State 2

State 3

XTAL

ALE

RD#/PSEN#

P0

A7:0

D7:0

A17/A16/P2

A17/A16/A15:8

A4230-01

Figure 13-3. External Data Read (Nonpage Mode)

13-4

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Intel 8XC251SQ, 8XC251SA, 8XC251SP, 8XC251SB manual Nonpage Mode Bus Cycles, External Code Fetch Nonpage Mode
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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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