8XC251SA, SB, SP, SQ USER’S MANUAL

Table B-2. Signal Descriptions (Continued)

Signal

Type

Description

Alternate

Name

Function

 

 

 

 

 

 

VSS2

GND

Secondary Ground 2. This ground is provided to reduce ground

—

 

 

bounce and improve power supply bypassing. Connection of this

 

 

 

pin to ground is recommended. However, when using the

 

 

 

8XC251SB as a pin-for-pin replacement for the 8XC51FX, VSS2 can

 

 

 

be unconnected without loss of compatibility. (Not available on

 

 

 

DIP.)

 

 

 

 

 

WAIT#

I

Real-time Wait State Input. The real-time WAIT# input is enabled

P1.6/CEX3

 

 

by writing a logical ‘1’ to the WCON.0 (RTWE) bit at S:A7H. During

 

 

 

bus cycles, the external memory system can signal ‘system ready’

 

 

 

to the microcontroller in real time by controlling the WAIT# input

 

 

 

signal on the port 1.6 input.

 

 

 

 

 

WCLK

O

Wait Clock Output. The real-time WCLK output is driven at port

P1.7/CEX4/A17

 

 

1.7 (WCLK) by writing a logical ‘1’ to the WCON.1 (RTWCE) bit at

 

 

 

S:A7H. When enabled, the WCLK output produces a square wave

 

 

 

signal with a period of one-half the oscillator frequency.

 

 

 

 

 

WR#

O

Write. Write signal output to external memory. Asserted for the

P3.6

 

 

memory address range specified by configuration byte UCONFIG0,

 

 

 

bits RD1:0 (Table B-3). Also see RD#.

 

 

 

 

 

XTAL1

I

Input to the On-chip, Inverting, Oscillator Amplifier. To use the

—

 

 

internal oscillator, a crystal/resonator circuit is connected to this pin.

 

 

 

If an external oscillator is used, its output is connected to this pin.

 

 

 

XTAL1 is the clock source for internal timing.

 

 

 

 

 

XTAL2

O

Output of the On-chip, Inverting, Oscillator Amplifier. To use

—

 

 

the internal oscillator, a crystal/resonator circuit is connected to this

 

 

 

pin. If an external oscillator is used, leave XTAL2 unconnected.

 

 

 

 

 

†The descriptions of A15:8/P2.7:0 and AD7:0/P0.7:0 are for the nonpage mode chip configuration (com- patible with 44-pin PLCC and 40-pin DIP MCS®51 microcontrollers). If the chip is configured for page mode operation, port 0 carries the lower address bits (A7:0), and port 2 carries the upper address bits (A15:8) and the data (D7:0).

B-6

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Intel 8XC251SB, 8XC251SA, 8XC251SP, 8XC251SQ, Embedded Microcontroller manual Dip Wait#, Wclk
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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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