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Microprocessor Articles
Page 31 of 42
Memory speed requirement in 8085 Microprocessor
At the end of the state T2 in a machine cycle, 8085 processor senses the Ready input pin. If it is logic 0, 8085 processors enter the Twait state, else it enters to the T3 state. The Ready input is permanently fixed to logic 1. The memory chips and the Input Output ports in the system same speed with 8085. Else appropriate number of wait states should be generated by the external circuit. In fact, in the ALS kit the Ready pin should be fixed to logic 1As an example, we check up if the 27128A-20 16K×8 EPROM chip are used ...
Read MoreEarliest data output time considering TACC in 8085 Microprocessor
27128 receives the Address A13-8 by 27128 from 8085AH by means of the octal line driver 74LS244, which has a propagation delay of 12 nS. Address ranging from A7-0 is received by 27128 from 8085AH by means of 74LS373 octal latch, which consists of a propagation delay of 30 nS. Thus, address ranging from A13-0 is received by 27128 at the end of 30 nS. So the data only comes out on D7-0 pins of 27128 by 30 nS + tAcc = 30 nS + 200 nS = 230 nS. Delays involved in accessing 27128 EPROM in ALS kit. Bus timing characteristics of MR machine cycle
Read MoreEarliest data output time considering TOE in 8085 Microprocessor
The 8085AH activates the RD* Signal at 270 nS. This signal moves to OE* pin of 27128 through the octal line driver 74LS241 delayed by 12nS. Hence the signal OE* signal is received by 27128 at the end of time 282 nS. Hence the data can only come out from the pins ranging from D7 to D0 of 27128 by 282 nS + tOE = 282 nS + 75 nS + 357 nS.From the discussion done previously it should be crystal clear that the earliest data output time should be 357 nS, by considering all the three parameters tACC, tCE, and ...
Read More27128-20 Compatibility check with 8085AH in 8085 Microprocessor
Let’s perform the memory compatibility check with respect to tAD, tLDR, and tRD parameters.Compatibility with respect to tAD: The time interval between valid address on the addresses ranging from A15 to A0 and valid data on the addresses ranges from AD7 to AD0. For 8085AH the T state working is 320 nS, but it consists of a maximum of 575 nS. But here the valid data is available for 365 nS. So the speed of the memory is compatible, with an excess time margin of 575 nS - 365 nS = 210 nS.Compatibility with respect to tLDR: The time interval between the edge of ...
Read MoreWait state generation in 8085 Microprocessor
The memory and the peripheral chips present today are very fast for a 8085 processor working at 3 MHz of frequency. So we do not need wait states. If we use 8085AH-2 which works at 5 MHz frequency, there we need to insert one wait state, between T2 and T3.To D-type positive edge-triggered flip flops are used by the circuit with an active low Reset inputs. At the beginning of T1, the Address Latch Enable goes very high and causes Q1 to go high. Since Q1 and D2 are connected, D2 remains very high throughout T1. The positive edge of ...
Read MorePrograms Using Interface Modules
We use a logic controller and it is used in industry for the process of control done by the software. Multiple inputs are typically accepted which performs a total complete sequence of operations carried out both arithmetic and logically. The outputs generated are used for the maintenance of the process within the specified desired limits. Visual display is provided by the state of process at any instant of time. The logic controller which interfaces and thus provides a buffered output of 12 lines and which is fed to the buffer inputs of 12 lines only specified for the user. The ...
Read MoreDescription of logic controller interface
We use a logic controller and it is used in industry for the process of control done by the software. Multiple inputs are typically accepted which performs a total complete sequence of operations carried out both arithmetic and logically. The outputs generated are used for the maintenance of the process within the specified desired limits. Visual display is provided by the state of process at any instant of time. The logic controller which interfaces and thus provides a buffered output of 12 lines and which is fed to the buffer inputs of 12 lines only specified for the user. The ...
Read MoreDecimal counter using logic controller
We write a program in the 8085 which is written in assembly language just for the implementation of a decimal counter which is used by the logic controller interface. The input of the starting count must be the input through the complete interface and moreover we display the count on the interface.Let us consider a sample program on this –The program which follows it should always contain an infinite loop until the inputs of the user contains a valid value of two-digit Binary Coded Decimal value just only to the Port B. After that the initial count gets displayed by ...
Read MoreEvaluation of Boolean expression
We write a program in 8085 in the assembly language just for the evaluation of only wo Boolean expressions of 4 variables by using the interface of logic controller. The output of the program should be logically tested automatically by the output by the input changing from the inputs from 0000, 0001, … to 1111 just to press any key.Let us say we want to evaluate the following Boolean expressions.First of all, truth table for the Boolean expressions is written down as shown in the following table.PQRSXY000010000100001010001100010010010100011010011100100001100101101010101100110000110111111000111100The inputs of the PQRS gets connected to PB3, PB2, PB1, and PB0 of ...
Read MoreSimulation of 4-bit ALU
Moreover, we write an assembly program in 8085 assembly language just to simulate a 4-bit ALU by using an interface which is based on the logic controller. The Arithmetic Logical Unit always performs an addition, subtraction, AND operation, or OR operation, which is based on the 4-bit inputs for the desired operations to be performed.For the simulation of the Arithmetic Logical Unit all the terminal inputs and outputs are provided by the ports of 8255 as it is indicated in the figure below.The Pins ranging from 7-4 in the Port B are used as the inputs of X3-0;The pins ranging ...
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