Data latch

A data latch can be built using JK flip-flops, clocked flip-flops, and all varieties of synchronous master-slave flip-flops (see Figure 23.17B). The clocked flip-flop data-latch operates in much the same way as the RS flip-flop data-latch the TP line must undergo a negative-going 1 to 0 transition each time data is transferred. However, the clocked flip-flop data-latch will operate only in a synchronous manner (that is, each time a negative-going clock pulse is present), in contrast to the RS flip-flop data-latch, in which the outputs will follow the inputs whenever the TP input is 0. 

Latches can, of course, be constructed for any number of data bits. Integrated-circuit data latches are commonly available in 4-bit, 8-bit, and larger configurations. 

Shift registers, like data latches, are often used for data storage, but they are much more versatile. They can acquire and output data in both serial and parallel modes and also move data within the register while it is being stored. 

Figure 23.17. Flip-flop data latches. From S. P. Perone and D. O. Jones, Digital Computers in Scientific Instrumentation, New York McGraw-Hill, 1973, by permission of the publisher. Copyright 1973 by McGraw-Hill, Inc.

Register Address. Register Enable. Multiplexer Data latch. 

A variable in Verilog HDL can either be of the net data type or the register data type. For synthesis, a variable of net type maps to a wire in hardware and a variable of the register type maps either to a wire or a storage element (flip-flop or latch) depending on the context under which the variable is assigned a value. Let us look at a variable of register type in more detail. 

Hinde I have an extremely naive question, just to set my mind at rest — I am sure it will just be brushed aside. We have heard a lot about how the different sorts of intelligence all latch onto g. Yet I know so many mathematicians who are almost illiterate, and so many literary people who are just about innumerate. Do you ever look at the distributions of these things Do you ever do categorical analysis All we hear about is correlation coefficients — Pearson s and Spearman s—and correlation coefficients are so misleading unless you categorize and eyeball your data. 

German and other European physicians also latched on to combination therapy of Proleukin with Interferon-alpha as helpful to outpatient or home care.35 A series of reports in German medical journals suggested that subcutaneous infusion and combination therapy would result in fewer side effects, less strain on patients, and more successful treatment of cancer.36 The approach drew sufficient interest from physicians that the company sponsored tests to document its efficacy and eventually presented data to the BGA supporting this method of application. Cetus used a database of 425 patients to compare 225 patients who received Proleukin as an intravenous drip infusion with 200 patients who injected themselves with Proleukin combined with Interferon-alpha. The two approaches did not result in statistically different outcomes in terms of cancer remission, but were strikingly different in their toxicity. Intravenous application had a remission rate of 15 percent, while 30 percent of the patients suffered from severe toxicity. In contrast, the subcutaneous application had a 20 percent remission rate with only 5 percent of patients experiencing severe toxicity.37... 

Latch window masking is related to the memory logic. Flip-flops are the main elements to store data within a circrrit (besides actual memory), and are commonly... 

Set-Reset Latch Truth Table Set-Reset Latch Macrotiming Diagram J K Latch T Latch D Latch Synchronous Latches Master-Slave Flip-Flops Standard Master-Slave Data Flip-Flop Sequential Logic System Description... 

A latch that stores the signal on an input data line is a data or D latch. A circuit that can accomplish this is shown in Fig. 1.65 along with its symbol representation and truth table. The D latch requires a second input, called a control signal and is sometimes a clock pulse, to control when the input signal is placed in storage. 

Most of the modern electronic systems are synchronous systems. The clock is a central pace setter in a synchronous system to step the desired system operations through various stages of the computation. Latches are often used to facilitate catching the output data at the end of each clock cycle. Figure 8.2 shows the typical synchronous circuit with random logic clusters as computational blocks and latches as pace setting devices. When there exist feedbacks, as shown in Fig. 8.2, the circuit is referred to as sequential circuit. 

When reading, a row address is given first, followed by the row address strobe signal RAS. RAS is used to latch the row address on chip. After RAS, a column address is given followed by the column address strobe CAS. After certain delay (read access time) valid data appear on the data Hnes. Memory write is done similarly to memory read with only the read/write control signal reversed. There are three cycles available to write a DRAM. They are early write, read-modify-write, and late write cycles. Figure 8.64 shows only the early write cycle of a DRAM chip. Other write cycles can be found in most of the DRAM databooks. 

Scan is a technique where storage elements (latches and flip-flops) are changed to dual mode elements. For instance, Fig. 8.125 shows a normal flip-flop of an integrated chcuit. Also shown in Fig. 8.125 is a flip-flop converted to a scan register element. During normal operation, the D input and system clock control the output of the flip-flop. During scan operation, the scan clocks are used to control shifting of data into... 

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