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Microprocessor Articles
Page 12 of 42
Vcc and Vss pins
VCC (Voltage Common Collector) is the higher voltage with respect to GND (ground). VCC is the power input of a device. It may be positive or negative with respect to GND. When the only positive power supply is used then VSS (Voltage Source Supply) means ground or zero. The Intel 8085 Microprocessor needs a power supply of +5 V DC for its working. Pin 40 of Intel 8085 is the Vcc pin. It should be connected to +5 V DC power supply. Pin 20 of 8085 is the Vss pin.
Read MoreBlock movement without overlap in Z-80
In this section, we will see how we can use the Zilog Z-80 Microprocessor to move a block of data to another location. There is one assumption, there is sufficient distance between source and destination. So blocks are non-overlapping. Basically the block movement is not exact moving, it is copying the data to other locations.The number of items in the block is given at location 5000H, and the block is located at position 5050H.So before movement, the items in the memory is looking like this.AddressValue5000H04H...5050H89H5051H7AH5052H2FH5053H56H...Now, we are writing a program at location 8000H to move the block contents to other ...
Read More8085 Program to Add two multi-byte BCD numbers
Now let us see a program of Intel 8085 Microprocessor. This program is mainly for adding multi-digit BCD (Binary Coded Decimal) numbers.Problem StatementWrite 8085 Assembly language program to add two multi-byte BCD (Binary Coded Decimal) numbers. DiscussionWe are using 4-byte BCD numbers. The numbers are stored into the memory at location 8501H and8505H. One additional information is stored at location 8500H. In this place, we are storing the byte count. The result is stored at location 85F0H.The HL pair is storing the address of first operand bytes, the DE is storing the address of second operand bytes. C is holding the ...
Read More8085 Program to Add N numbers, of size 8 bits
In this program, we will see how to add a block of data using the 8085 microprocessor.Problem StatementWrite 8085 Assembly language program to add N 1-byte numbers. The value of N is provided.DiscussionIn this problem, we are using location 8000H to hold the length of the block. The main block is stored from address 8010H. We are storing the result at location 9000H and 9001H. The 9000H holding the lower byte, and 9001H is holding the upper byte.Repeatedly we are taking the number from the memory, then adding it with the accumulator and increase the register E content when carry ...
Read MoreRegister codes of 8085 Microprocessor
Using 16-bit address, 8085 can access one of the 216= 64K locations. As a single hexadecimal digit can be expressed in4-bit notation so, in 8085, memory address can be expressed using four hexadecimal digits. Similarly, for convenience, we can represent all 8085 CPU registers as A, B, C etc. using binary notations. Internally 8085 specifies these registers using 0s and 1s only. So3-bits are just enough to represent a register. The 3-bit register codes for the registers of 8085 are shown in the following tableWith 3-bit register code, eight registers can be specified in maximum as 23= 8. On the ...
Read MoreAbsolute addressing mode in 8085 Microprocessor
In this mode, the data is directly copied from the given address to the register. This absolute addressing mode is also called a direct addressing mode. For example LDA 3000H: means the data at address 3000H is copied to register A.LDA 4050HLet us consider LDA 4050 Has an example instruction of this type. It is a 3-Byte instruction. The initial content of memory address 4050H is ABH. initial accumulator content is CDH. As after execution A will be initialized with value ABH. Memory location 4050H will still remain with the content ABH. The results of the execution of this instruction ...
Read MoreIntel 8259A Programmable Interrupt Controller
8085 microprocessor, consists of five interrupt input pins named as RST 5.5, RST 6.5, RST7.5, INTR, and TRAP respectively. When there are a maximum of five I/O devices they want to perform driven interrupt data transfer, which is connected to the five interrupt input pins. Now considering the case where there are more than five I/O devices which would like to perform an interrupt driven data transfer scheme. Here for some pins termed as an interrupt, we use more than one I/O device to the process. Most of the microprocessors nowadays have the configuration of these interrupt input pins. There ...
Read MoreInterrupt mask register in 8259
It stores the levels of interrupts to be masked by means of storing the bits of the interrupt level already masked. It differs from other registers by means of only masking of the bits. Other processes remained intact. Let’s take for the assumption that the requests to the IR4 AND IR6 should not be an interrupt to the processor which can be well achieved by setting the bits of IMR to 1. The IMR is written by OCW1 command. The processor here also has the capability to read the contents of the IMRregister. To complete this task, the processor has ...
Read MoreIn-service register in 8259
Also, an 8-bit register which keeps track records of the interrupt requests that are currently being executed. If the request IR6 is currently being served, whose contents of ISR will be 01000000. If by any means the request to IR3 becomes active during the service process of IR6, 8259 sets bit 3 of ISR to 1 and activates the output INT. But bit 6 of ISR always remains set at 1 asIR6 request which is not fully serviced. Hence the contents ofISR become 01001000. The following assumptions stated below helps this to happen.Until 8259 operates in a complete nested mode, without ...
Read MoreSlave register in 8259
It is also an 8-bit register. The processor here writes to SLR but cannot read. The content of this register here implies a different meaning for Master8259 and Slave 8259. Through Master 8259 information is carried through the IR inputs to which Slave 8259s are connected. If the SLR of Master 8259 is loaded with the value 00001111, then it signifies that:The Slave exists on 8259 namely called as IR0, IR1, IR2 and IR3.No Slave exists on 8259 on this registers IR4, IR5, IR6 and IR7.A Slave 8259 serves information about the IR input of Master 8259 to which the ...
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