TIMER/COUNTERS AND WATCHDOG TIMER

8.3.3Mode 2 (8-bit Timer With Auto-reload)

Mode 2 configures timer 0 as an 8-bit timer (TL0 register) that automatically reloads from the TH0 register (Figure 8-3). TL0 overflow sets the timer overflow flag (TF0) in the TCON register and reloads TL0 with the contents of TH0, which is preset by software. When the interrupt re- quest is serviced, hardware clears TF0. The reload leaves TH0 unchanged. See section 8.5.1, “Auto-load Setup Example.”

XTAL1

12

 

 

 

 

0

 

 

Interrupt

 

TLx

Overflow

Request

 

 

TFx

 

1

(8 Bits)

 

 

 

 

Tx

 

 

 

 

 

C/Tx#

 

 

 

TRx

 

 

Reload

 

 

 

 

 

GATEx

 

THx

 

 

 

(8 Bits)

 

 

 

 

 

 

INTx#

 

x = 0 or 1

 

 

 

 

 

 

A4111-02

Figure 8-3. Timer 0/1 in Mode 2, Auto-Reload

8.3.4Mode 3 (Two 8-bit Timers)

Mode 3 configures timer 0 such that registers TL0 and TH0 operate as separate 8-bit timers (Fig- ure 8-4). This mode is provided for applications requiring an additional 8-bit timer or counter. TL0 uses the timer 0 control bits C/T0# and GATE0 in TMOD, and TR0 and TF0 in TCON in the normal manner. TH0 is locked into a timer function (counting FOSC /12) and takes over use of the timer 1 interrupt (TF1) and run control (TR1) bits. Thus, operation of timer 1 is restricted when timer 0 is in mode 3. See section 8.4, “Timer 1,” and section 8.4.4, “Mode 3 (Halt).”

8.4TIMER 1

Timer 1 functions as either a timer or event counter in three modes of operation. Figures 8-2 and 8-3 show the logical configuration for modes 0, 1, and 2. Timer 1’s mode 3 is a hold-count mode.

8-5

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Intel Embedded Microcontroller, 8XC251SA, 8XC251SP, 8XC251SQ Mode 2 8-bit Timer With Auto-reload, Mode 3 Two 8-bit Timers
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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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