Alternate Port Usage, Pca Timer/Counter | Intel 8XC251SP, 8XC251SA

8XC251SA, SB, SP, SQ USER’S MANUAL

9.1.1Alternate Port Usage

PCA modules 3 and 4 share port pins with the real-time wait state and address functions as fol- lows:

•PCA module 3 — P1.6/CEX3/WAIT#

•PCA module 4 — P1.7/CEX4/A17/WCLK

When the real-time wait state functions are enabled (using the WCON register), the correspond- ing PCA modules are automatically disabled. Configuring the 8XC251Sx to use address line A17 (specified by UCONFIG0, bits RD1:0) overrides the PCA module 3 and WCLK functions. When a real-time wait state function is enabled, do not use the corresponding PCA module.

NOTE

It is not advisable to alternate between PCA operations and real-time wait state operations at port 1.6 (CEX3/WAIT#) or port 1.7 (CEX4/WCLK). See section 13.5, “External Bus Cycles with Real-time Wait States.”

9.2PCA TIMER/COUNTER

Figure 9-1 depicts the basic logic of the timer/counter portion of the PCA. The CH/CL special function register pair operates as a 16-bittimer/counter. The selected input increments the CL (low byte) register. When CL overflows, the CH (high byte) register increments after two oscil- lator periods; when CH overflows it sets the PCA overflow flag (CF in the CCON register) gen- erating a PCA interrupt request if the ECF bit in the CMOD register is set.

The CPS1 and CPS0 bits in the CMOD register select one of four signals as the input to the timer/counter (Figure 9-7).

•FOSC/12. Provides a clock pulse at S5P2 of every peripheral cycle. With FOSC = 16 MHz, the time/counter increments every 750 nanoseconds.

•FOSC/4. Provides clock pulses at S1P2, S3P2, and S5P2 of every peripheral cycle. With FOSC = 16 MHz, the time/counter increments every 250 nanoseconds.

•Timer 0 overflow. The CL register is incremented at S5P2 of the peripheral cycle when timer 0 overflows. This selection provides the PCA with a programmable frequency input.

•External signal on P1.2/ECI. The CPU samples the ECI pin at S1P2, S3P2, and S5P2 of every peripheral cycle. The first clock pulse (S1P2, S3P2, or S5P2) that occurs following a high-to-low transition at the ECI pin increments the CL register. The maximum input frequency for this input selection is FOSC/8.

For a description of peripheral cycle timing, see section 2.2.2, “Clock and Reset Unit.”

9-2

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 8XC251SP, 8XC251SA, 8XC251SQ, 8XC251SB manual Alternate Port Usage, Pca Timer/Counter

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