Pwr, Dip, Gnd | Intel 8XC251SQ, 8XC251SA, 8XC251SP, 8XC251SB

SIGNAL DESCRIPTIONS

Table B-2. Signal Descriptions (Continued)

Signal	Type	Description	Alternate
Name	Type	Description	Function
Name			Function

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 sends and receives data in serial I/O	P3.0
		mode 0 and receives data in serial I/O modes 1, 2, and 3.

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 the timer 2 capture mode, this	P1.0
		signal is the external clock input. For the clock-out mode, it is the
		timer 2 clock output.

T2EX	I	Timer 2 External Input. In timer 2 capture mode, a falling edge	P1.1
		initiates a capture of the 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	P3.1
		mode 0 and transmits serial data in serial I/O modes 1, 2, and 3.

VCC	PWR	Supply Voltage. Connect this pin to the +5V supply voltage.	—
VCC2	PWR	Secondary Supply Voltage 2. This supply voltage connection is	—
		provided to reduce power supply noise. Connection of this pin to
		the +5V supply voltage 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.)

VPP	I	Programming Supply Voltage. The programming supply voltage	EA#
		is applied to this pin for programming on-chip nonvolatile memory.

VSS	GND	Circuit Ground. Connect this pin to ground.	—
VSS1	GND	Secondary Ground. 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
		8XC251SA, SB, SP, SQ as a pin-for-pin replacement for the
		8XC51BH, VSS1 can be unconnected without loss of compatibility.
		(Not available on DIP.)

†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-5

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.

Intel 8XC251SQ, 8XC251SA, 8XC251SP, 8XC251SB, Embedded Microcontroller manual Pwr, Dip, Gnd

Models: Embedded Microcontroller 8XC251SP 8XC251SA 8XC251SQ 8XC251SB

Signal

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

PWR

DIP.)

EA#

GND

Embedded Microcontroller, 8XC251SP, 8XC251SA, 8XC251SQ, 8XC251SB specifications