Found 475 Articles for 8085

So far we have come across OF, MR, MW, IOR, and IOW machine cycles. The other possible machine cycles in 8085 are BI (bus idle) and INA (interrupt acknowledge) machine cycles. Now the differences between some of the machine cycles are presented in the following tables.Difference between OF and MR1. Number of T states in case for OF is 4, Number of T states in case for MR is 32. In case of OF address can be sent out from PC. Whereas in case of MR it can be sent from BC, PC, DE, HL etc.3. In case of OF, ... Read More

The three clock cycles at the last stages in the IN 35H instruction is an example of machine cycle for IOR. The Waveforms for the IOR machine cycle are shown in the figure below.The point to be noted that in an IOR machine cycle, Wand Z has identical has port address of 8 bit. The value of 16 bit in the register pair WZ are sent out as the address in an Input Output Read machine cycle. Also the point to be noted that in an IOR machine cycle, only the data is received by the accumulator from the addressed ... Read More

The last three clock cycles in the OUT 25H instruction is an example for IOW machine cycle. Waveforms for IOW machine cycle are shown in the figure below: The point to be noted that in an IOW machine cycle, Wand Z registers have identical 8-bit port address. There is also a definite advantage because of address duplication on the addresses ranging from A15-8 and AD7-0 when we are using 8755 (2K × 8 EPROM and two 8-bit ports) and 8155 which is a combination of 256 × 8 RAM, 3 Input Output ports, and 14-bit timer. We can form a 8085-based ... Read More

In the last three clock cycles the instructions ‘MVI M, 25H’ are the example for Memory Write machine cycle. We have shown the Waveforms for MW machine cycle are shown in fig below.The address which is sent out from the register pair in a Memory Write machine cycle is completely dependent on the MW machine cycle under the consideration as it is shown in the chart below.Reg. pairExampleSPWe push the information above the top of the stack in PUSH BHLWe save register C in the memory which is pointed by HL in MOV M, CBCWe save register A register in the ... Read More

The last three clock cycles in ‘MOV C, M’ instruction are the example for Memory Read machine cycle. Waveforms for Machine Read machine cycle is shown below: InstructionOperationAddress reg.LDA 1234HLoading W with 12H (or Z with 34H)PCPOP BPopping information from stack topSPMOV C, MLoading A from memory pointed by HLHLLDAX BLoading A from memory pointed by BCBCLDAX DLoading A from memory pointed by DEDELDA 1234HLoading A from memory Location 1234HWZ The data, which is received in a register during a Memory Read machine cycle depends on the MR machine cycle within an instruction as shown below. Where ‘r’ stands for any of ... Read More

The OF machine cycle are constituted by the four clock cycles shown in the figure below. Here in these four clock cycles we execute opcode fetch, decode, and complete the execution. Moreover, in the instructions of 2- and 3-byte, and also in the instructions of 1 byte like ‘MOV B, M’, only OF and decode operations gets completed in these four cycles of the clock. Hence opcode fetch is consisted by the OF machine cycle and for performing the decode operation, and in some rare cases execution. For performing some typical instructions like DCX B, the six states are provided ... Read More

In a matrix keyboard there are keys which are arranged in the form of a matrix which consists of several rows and columns. In the figure which is stated below significantly indicates the interfacing process of a matrix keyboard which consists four rows and four columns respectively. We connect a key at the intersection of every rows and columns. Hence there is a total of 4 × 4 = 16 keys in the given matrix. The lines of the columns get connected to Gnd through pull-down resistors.Even there is a matrix size were to be 8 × 8, for a sum ... Read More

A keyboard is a very common input device. We assume that there are only eight keys for the simple keyboard. Whenever a key is pressed on this keyboard by the user, the microprocessor immediately identifies which key is pressed. The action which is to be performed by the processor depends on that particular key that gets pressed. An example to be cited as on a particular keyboard for calculator the addition operation gets performed when we press the ‘+’ key. Moreover, a microprocessor does not get directly communicated by the input device it is done via the input port. The ... Read More

Intel 8279 is a specially designed Input Output port chip which performs two major functions. It scans a matrix keyboard, as well as it displays a multiplexed display such that the processor gets relieved from the extreme tasks and let it performs systematically. We had given a brief description about the working of 8279 as we have indicated in the following paragraphs.We continuously scan an 8279 matrix keyboard. During the scanning process, if a key gets pressed on the keyboard a scanning is performed again about 10 μs, resulting bouncing of the key to die down. If it is found ... Read More

In this module we have explained the complete interface of four numbers segmented into seven parts having the Light Emitting Diode which uses a serial data transfer scheme. The portion which is displayed of the interface has 4 LEDS comprises of 7-segments LEDs as we can see from the physical layout of the interface. The connection to the interface is done by the ALS-8085 kit which uses a flat table of 26 crores. We connect the connector C1 to the interface to the Input Output connector P3 on the ALS kit. There is a power supply of of +5 V ... Read More