SUMMARY off INTRODUCTION TO Z80 INSTRUCTIONS AND PROGRAMMING TECHNIQUES

By -

SUMMARY off INTRODUCTION TO Z80 INSTRUCTIONS AND PROGRAMMING TECHNIQUES

 

cvjg

In this chapter, we illustrated a group of instructions from the Z80 set frequently used in writing programs. Instructions were selected from three groups: data copy, arithmetic, and branch. These instructions range from 1 byte to 4 bytes long. General characteristics of these instructions are as follows:

1. The data copy and load instructions copy the contents of the source into the destination without affecting the source contents. They do not affect the flags.

2. The arithmetic instructions (with some exceptions) assume one of the oper­ands is the accumulator, and the result of an operation is usually stored in the accumulator. Most of these instructions affect the flags.

3. The conditional Jump instructions are decision-making instructions and are executed according to the status of the flags. Not all instructions affect the flags; in particular, the data copy instructions and 16-bit increment/decrement instructions do not affect the flags.

4. The Z80 microprocessor includes two index registers (IX and IY), which are used primarily as memory pointers. The instructions related to index regis­ters have 2-byte Opcode and perform data copy and arithmetic operations with the contents of memory registers.

Programming techniques such as looping, counting, and indexing were dis­cussed and a generalized flowchart was illustrated. Two illustrative programs were discussed in the context of this generalized flowchart.

Finally, some Z80 special instructions were introduced. These instructions perform multiple tasks; thus, they improve programming efficiency.

Comments

Post a Comment

Popular posts from this blog

80386 pins and signals , 80386 modes , 80386 system design and 80386 i/o

By -
Image
11.3.5 80386 Pins and Signals The 80386 contains 132 pins in Pin Grid Array (PGA) or other packages. Figure 11.2 shows functional grouping of the 80386 pins. A brief description of the 80386 pins and signals is provided in the following. The # symbol at the end of the signal name or the- symbol above a signal name indicates the active or asserted state when it is low. When the symbol # is absent after the signal name or the symbol- is absent above a signal name, the signal is asserted when high. The 80386 has 20 Vcc and 21 GND pins for power distribution. These multiple power and ground pins reduce noise. Preferably, the circuit board should contain VCC and GND planes. CLK2 pin provides the basic timing for the 80386. This clock is then divided by 2 by the 80386 internally to provide the clock used for instruction execution. The 80386 is reset by activating the RESET pin for at least 15 CLK2 periods. The RESET signal is level­ sensitive. When the RESET pin is asserted, the 8038...
Read more

Multi-Tasking and Real-Time Operating Systems:Random Number Generator

By -
Image
PROJECT 10.2—Random Number Generator In this slightly more complex RTOS project, a random number between 0 and 255 is generated. Eight LEDs are connected to PORTB of a PIC18F452 microcontroller. In addition, a push-button switch is connected to bit 0 of PORTD (RD0), and an LED is connected to bit 7 of PORTD (RD7). Three tasks are used in this project: Live, Generator, and Display. • Task Live runs every 200ms and flashes the LED on port pin RD7 to indicate that the system is working. • Task Generator increments a variable from 0 to 255 continuously and checks the status of the push-button switch. When the push-button switch is pressed, the value of the current count is sent to task Display using a messaging queue. • Task Display reads the number from the message queue and sends the received byte to the LEDs connected to PORTB. Thus, the LEDs display a random pattern every time the push button is pressed. Figure 10.9 shows the project’s block diagram. The circuit diagram is ...
Read more

Advanced PIC18 Projects—SD Card Projects:Using the Card Filing System

By -
Image
PROJECT 7.3—Using the Card Filing System The hardware of this project is the same as for Project 7.1 (i.e., as shown in Figure 7.8). In this project, a file called MYFILE55.TXT is created on the SD card. String “This is MYFILE.TXT” is written to the file initially. Then the string “This is the added data.. .” is appended to the file. The program then reads the contents of the file and sends the string “This is MYFILE.TXT. This is the added data.. .” to the UART, enabling the data to be displayed on the PC screen when HyperTerminal is run. The program listing of the project is given in Figure 7.12 (program SD3.C). At the beginning of the program the UART is initialized to 2400 baud. Then the SPI bus and the FAT file system are initialized as required by the library. The program then creates file MYFILE55.TXT by calling library function Mmc_Fat_Assign with the arguments as the filename and the creation flag 0x80, which tells the function to create a new file if the file doe...
Read more