Djnz 40H,LABEL1 Djnz 50H,LABEL2 Djnz 60H,LABEL

8XC251SA, SB, SP, SQ USER’S MANUAL

Example: The on-chip RAM locations 40H, 50H, and 60H contain 01H, 70H, and 15H, respectively. After executing the following instruction sequence

DJNZ 40H,LABEL1

DJNZ 50H,LABEL2

DJNZ 60H,LABEL

on-chip RAM locations 40H, 50H, and 60H contain 00H, 6FH, and 14H, respectively, and program execution continues at label LABEL2. (The first jump was not taken because the result was zero.)

This instruction provides a simple way of executing a program loop a given number of times, or for adding a moderate time delay (from 2 to 512 machine cycles) with a single instruction.

The instruction sequence,

MOV R2,#8

TOGGLE: CPL P1.7

DJNZ R2,TOGGLE

toggles P1.7 eight times, causing four output pulses to appear at bit 7 of output Port 1. Each pulse lasts three states: two for DJNZ and one to alter the pin.

Variations

DJNZ dir8,rel

	Binary Mode		Source Mode
	Not Taken	Taken	Not Taken	Taken
Bytes:	3	3	3	3
States:	3	6	3	6

[Encoding]

1 1 0 1

0 1 0 1

direct addr

rel. addr

Hex Code in: Binary Mode = [Encoding]

Source Mode = [Encoding]

Operation: DJNZ

(PC) ← (PC) + 2 (dir8) ← (dir8) – 1

IF (dir8) > 0 or (dir8) < 0

THEN

(PC) ← (PC) + rel

DJNZ Rn,rel

	Binary Mode		Source Mode
	Not Taken	Taken	Not Taken	Taken
Bytes:	2	2	3	3
States:	2	5	3	6

[Encoding]

1 1 0 1

1 r r r

rel. addr

Hex Code in: Binary Mode = [Encoding] Source Mode = [A5][Encoding]

A-58

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 8XC251SA Djnz 40H,LABEL1 Djnz 50H,LABEL2 Djnz 60H,LABEL, Toggle CPL P1.7 Djnz R2,TOGGLE

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