8xC251Tx Hardware Description

Table 2. 8xC251Tx Signal Descriptions (Sheet 2 of 3)

Signal

Type

 

Description

Alternate

Name

 

Function

 

 

 

 

 

 

 

P3.0

I/O

Port 3. This is an 8 bit, bidirectional I/O port with internal pullups

RXD

P3.1

 

 

 

TXD

P3.2

 

 

 

INT0#

P3.3

 

 

 

INT1#

P3.4

 

 

 

T0

P3.5

 

 

 

T1

P3.6

 

 

 

WR#

P3.7

 

 

 

RD#/A16

 

 

 

 

PSEN#

O

Program Store Enable. Read signal output to external memory.

 

 

 

Asserted for the address range specified by the configuration byte

 

 

 

UCONFIG0, bits RD1:0.

 

 

 

 

 

RD#

O

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

P3.7/A16

 

 

address range specified by the configuration byte UCONFIG0, bits

 

 

 

RD1:0.

 

 

 

 

 

RST

I

Reset. Reset input to the chip. Holding this pin high for 64 oscillator

 

 

 

periods while the oscillator is running resets the device. The port pins

 

 

 

are driven to their reset conditions when a voltage greater than VIH1

 

 

 

is applied, whether or not the oscillator is running. This signal has a

 

 

 

Schmitt trigger input. Connecting the RST pin to VCC through a

 

 

 

capacitor provides power-on reset. Asserting RST when the chip is in

 

 

 

idle mode or powerdown mode returns the chip to normal operation.

 

 

 

 

 

RXD

I/O

Receive Serial Data. RXD send and receives data in serial I/O mode

P3.0

 

 

0 and receives data in serial I/O modes 1, 2 and 3.

 

 

 

 

 

RXD1

I/O

Receive Serial Data 1. RXD send and receives data in serial I/O

P1.2/ECI

 

 

mode 0 and receives data in serial I/O modes 1, 2 and 3 for the sec-

 

 

 

ond serial I/O port.

 

 

 

 

 

T1:0

I

Timer 1:0 External Clock Inputs. When Timer 1:0 operates as a

P3.5:4

 

 

counter, a falling edge on the T1:0 pin increments the count.

 

 

 

 

 

T2

I/O

Timer 2 Clock Input/Output. For Timer 2 capture mode, this signal

P1.0

 

 

is the external clock input. For the clock-out mode, it is the timer 2

 

 

 

clock input.

 

 

 

 

 

T2EX

I

Timer 2 External Input. In Timer 2 capture mode, a falling edge ini-

P1.1

 

 

tiates a capture of Timer 2 registers. In auto-reload mode, a falling

 

 

 

edge causes the Timer 2 registers to be reloaded. In the up-down

 

 

 

counter mode, this signal determines the count direction:

 

 

 

•

1=up

 

 

 

•

0 = down.

 

 

 

 

 

TXD

O

Transmit Serial Data. TXD outputs the shift clock in serial I/O mode

P3.1

 

 

0 and transmits serial data in serial I/O modes 1, 2 and 3.

 

 

 

 

 

TXD1

O

Transmit Serial Data 1. TXD outputs the shift clock in serial I/O

P1.3/CEX0

 

 

mode 0 and transmits serial data in serial I/O modes 1, 2 and 3 for the

 

 

 

second serial I/O port.

 

 

 

 

 

VCC

PWR

Supply Voltage. Connect this pin to the +5 supply voltage.

 

*The descriptions of A15:8/P2.7:0 and AD7:0/P0.7:0 are for non page mode configuration. If configured in page mode, Port 0 carries the lower address bits (A7:0) and Port 2 carries the upper address bits (A15:8) and the data (D7:0)

4

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Intel 8xC251TQ, 8xC251TB XC251Tx Signal Descriptions Sheet 2, Timer 10 External Clock Inputs. When Timer 10 operates as a
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8XC251SP, 8XC251SA, 8XC251SQ, 8xC251TB, 8xC251TQ 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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