Write a short note on read only memory pdf

Long Streams of Lots of Images, Video sequences To process an image, you not only need operators to work on the images, but you also need ways to read in and write out the image in as many different file formats as possible. In this section we look at IM file formats in general. Image Formats Summary One of the most common uses of ImageMagick is not to modify images at all, but only to convert an image from one image format to another.

Write a short note on read only memory pdf

The time required to discharge a capacitor thus depends on what logic value is stored in the capacitor. A capacitor containing logic one begins to discharge when the voltage at the access transistor's gate terminal is above VCCP. If the capacitor contains a logic zero, it begins to discharge when the gate terminal voltage is above VTH.

The drive to increase both density, and to a lesser extent, performance, required denser designs.

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The minimization of DRAM cell area can produce a denser device which could be sold at a higher priceor a lower priced device with the same capacity. Starting in the mids, the capacitor has been moved above or below the silicon substrate in order to meet these objectives.

DRAM cells featuring capacitors above the substrate are referred to as stacked or folded plate capacitors; whereas those with capacitors buried beneath the substrate surface are referred to as trench capacitors.

In the s, manufacturers were sharply divided by the type of capacitor used by their DRAMs, and the relative cost and long-term scalability of both designs has been the subject of extensive debate.

The majority of DRAMs, from major manufactures such as HynixMicron TechnologySamsung Electronics use the stacked capacitor structure, whereas smaller manufacturers such Nanya Technology use the trench capacitor structure Jacob, pp. The capacitor in the stacked capacitor scheme is constructed above the surface of the substrate.

The capacitor is constructed from an oxide-nitride-oxide ONO dielectric sandwiched in between two layers of polysilicon plates the top plate is shared by all DRAM cells in an ICand its shape can be a rectangle, a cylinder, or some other more complex shape. There are two basic variations of the stacked capacitor, based on its location relative to the bitline—capacitor-over-bitline COB and capacitor-under-bitline CUB.

In a former variation, the capacitor is underneath the bitline, which is usually made of metal, and the bitline has a polysilicon contact that extends downwards to connect it to the access transistor's source terminal. In the latter variation, the capacitor is constructed above the bitline, which is almost always made of polysilicon, but is otherwise identical to the COB variation.

The advantage the COB variant possesses is the ease of fabricating the contact between the bitline and the access transistor's source as it is physically close to the substrate surface. However, this requires the active area to be laid out at a degree angle when viewed from above, which makes it difficult to ensure that the capacitor contact does not touch the bitline.

CUB cells avoid this, but suffer from difficulties in inserting contacts in between bitlines, since the size of features this close to the surface are at or near the minimum feature size of the process technology Kenner, pp.

The trench capacitor is constructed by etching a deep hole into the silicon substrate. A layer of oxide-nitride-oxide dielectric is grown or deposited, and finally the hole is filled by depositing doped polysilicon, which forms the top plate of the capacitor.

write a short note on read only memory pdf

The top the capacitor is connected to the access transistor's drain terminal via a polysilicon strap Kenner, pp. A trench capacitor's depth-to-width ratio in DRAMs of the mids can exceed Trench capacitors have numerous advantages. Since the capacitor is buried in the bulk of the substrate instead of lying on its surface, the area it occupies can be minimized to what is required to connect it to the access transistor's drain terminal without decreasing the capacitor's size, and thus capacitance Jacob, pp.

Alternatively, the capacitance can be increased by etching a deeper hole without any increase to surface area Kenner, pg. Another advantage of the trench capacitor is that its structure is under the layers of metal interconnect, allowing them to be more easily made planar, which enables it to be integrated in a logic-optimized process technology, which have many levels of interconnect above the substrate.

The fact that the capacitor is under the logic means that it is constructed before the transistors are. This allows high-temperature processes to fabricate the capacitors, which would otherwise be degrading the logic transistors and their performance.

Disadvantages of trench capacitors are difficulties in reliably constructing the capacitor's structures within deep holes and in connecting the capacitor to the access transistor's drain terminal Kenner, pg.

By the second-generation, the requirement to increase density by fitting more bits in a given area, or the requirement to reduce cost by fitting the same amount of bits in a smaller area, lead to the almost universal adoption of the 1T1C DRAM cell, although a couple of devices with 4 and 16 Kbit capacities continued to use the 3T1C cell for performance reasons Kenner, p.

These performance advantages included, most significantly, the ability to read the state stored by the capacitor without discharging it, avoiding the need to write back what was read out non-destructive read.

A second performance advantage relates to the 3T1C cell has separate transistors for reading and writing; the memory controller can exploit this feature to perform atomic read-modify-writes, where a value is read, modified, and then written back as a single, indivisible operation Jacob, p.

Proposed cell designs[ edit ] The one-transistor, zero-capacitor 1T DRAM cell has been a topic of research since the lates.

Write-only memory (joke) - Wikipedia

In 1T DRAM cells, the bit of data is still stored in a capacitive region controlled by a transistor, but this capacitance is no longer provided by a separate capacitor. Considered a nuisance in logic design, this floating body effect can be used for data storage. This gives 1T DRAM cells the greatest density as well as allowing easier integration with high-performance logic circuits, since they are constructed with the same silicon on insulator process technologies.

Array structures[ edit ] DRAM cells are laid out in a regular rectangular, grid-like pattern to facilitate their control and access via wordlines and bitlines. The physical layout of the DRAM cells in an array is typically designed so that two adjacent DRAM cells in a column share a single bitline contact to reduce their area.Write-only memory (WOM) is the opposite of read-only memory (ROM).

By some definitions, a WOM is a memory device which can be written but never read. By some definitions, a WOM is a memory device which can be written but never read. Memory and Programmable Logic 1. Random-Access Memory and data in current use are kept so that they can be q uickly reached by the computer's processor.

2. Read-Only Memory (ROM): ROM is a type of memory that is as fast as RAM, but has two important A 0 in the read/write input provides the write operation by forming a path from the.

Read-only memory (ROM) is a type of non-volatile memory used in computers and other electronic devices. Data stored in ROM can only be modified slowly, Write-only memory; Terminology.

EEPROM: electrically erasable programmable read-only memory can be reprogrammed and reused many times;. A Brief Summary of Common Image File Formats For a introduction to reading and writing image formats see Image File schwenkreis.com a list of all the ImageMagick file formats are given on the IM Image Formats Page..

Here is a very quick summary of the most common 'normal' image file formats, as well as their general advantages and disadvantages. BCLK LRCLK 0 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 15 DIN/ DOUT 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 15 MSB LSB MSB LSB MSB Left Channel Right Channel Left-JustifiedMode schwenkreis.com .

DESCRIPTION The Signetics Series 9C46XN Random Access Write-Only-Memory employs both enhancement and depletion mode P-Channel, N-Channel and Neu(1) channel MOS devices. Although a static device, a single TTL level clock phase is.

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