Digis The trouble is it has a fluorescent display and few c64 processors can drive it directly. It is very easy to convert the bit pattern from binary to hexadecimal. Similar Threads Eprom programming help 8. Would you have a minute to take a look at a file i have produced in regards this. This means only of the possible EPROM addresses are actually used and although not marked on the schematic, address lines A8 upward are all unused and tied to ground.

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If you divide , by 8 number of bits in a byte you get 32, or 32K K is an abbreviation for kilo or thousand. For example the 27C stores 4 million bits or K bytes of data. The access time is specified in nanoseconds billionths of a second. The access time is usually found following the part number. The access time is normally found after the dash - which separates the part number from the access time.

When you replace an EPROM or any memory device, you may substitute a part of equal or faster speed but not one of slower speed. The data can be available from the EPROM before it is needed however if the CPU attempts to take the data before it is there, the product the computer is in will not work. Figuring out the part number on your chip EPROMs and most other memory parts conform to a standard pin configuration and operate in an identical manner. This allows parts from any manufacturer to be used interchangably.

The key is to figure out the part number on your device. Usually the part number is printed directly on the top of the part. What you are looking for is the core part number. This is the industry standard number for the part. This number may have a prefix or suffix associated with it. The part number on the chip is HNG. Note where the appears HNG. A date code is printed on the chip to indicate when it was manufactured. A date code is the year of manufacture followed by the week.

An example would be This indicates that the part was manufactured in the 25th week of Although a date code is not easily confused for a 27XXX chip, it can be for other types of memory parts which are not 27XXX devices. There is one transistor for each bit of storage.

The programming process forces the charge on the transistor where it remains trapped until the part is erased. A charged programmed transistor holds the bit value of 0 where an erased unprogrammed transistor holds the bit value of 1. The purpose of this window is to allow the ultraviolet light to reach the transistors which compose the EPROM memory array and dissipate the electrons trapped on the transistors.

You cannot erase an EPROM or change its contents by removing this cover and exposing it to normal room light. Even in direct sunlight it would take two weeks of constant exposure to alter the chip. What is the difference between a 27 and a 27C part? The technology process is called NMOS. This is especially true in battery powered equipment.

Different package types There are several package types into which memory parts or microcontrollers are found. The traditional package, which has been shown throughout this page, is called a DIP. It is so called because it has two rows of pins which insert into a socket or holes in the circuit board.

The primary advantage of this package is that it is easily removed and installed by humans. In reality, the actual memory chip is much smaller than the package into which it is placed. DIP packages can be of any size between 8 and 42 pins. The 40 pin package is used because the data is read 16 bits at a time and thus requires more physical pins to connect to the processor. In order to conserve space there are several package styles which have become common.

One is the PLCC. PLCC packages have the primary advantage of size. With electronic products becoming increasingly small, designers use PLCC parts for surface-mount or space limited designs. There are sockets available for PLCC parts, however they require a special tool to remove the device.

If the PLCC part is soldered directly to the board, the part must be desoldered before it can be read. A special adapter is required to use a PLCC part with a device programmer. The device shown in the photo is a 29FT flash memory part. One of the smallest package styles available is the TSOP. A special adapter is required to support these devices. The adapter socket has tiny retractable contacts which mate with each fine-pitch device lead. These parts are always in plastic cases because the erasing of the part is done electrically without the need to expose the internal chip to ultraviolet light.

Flash memory parts cannot be substituted for a standard UV erasable part because the minimum number of pins on a typical flash part is Unlike Flash devices, these memory parts can have individual bytes changed without the need to erase the entire part.

The way this works is that the memory chip itself performs an erase on a single byte before programming the byte with the new data. The erase and program of a single byte can take as long as 10 milliseconds.

EEPROMs are normally used for data storage in a product since they can be "written to" by the computer.

This is because the address and data are sent to and from the chip one bit at a time using two or three wires. In order for the computer to read and write the serial EEPROM it must actually send commands, data and address information via a predefined communication protocol. This takes more time and is more complex than dealing with a larger EEPROM, however the cost and size savings make these parts very popular where the amount of information which must be stored is small.

SPI part numbers start with 25 or These parts are very common and used in many applications including automotive. These packages are very small and are always soldered directly to a circuit board. Under many circumstances it is possible to connect to these parts " in-circuit " and successfully read and program information. The NV stands for non-volatile. The RAM would normally lose its contents when power is removed, however the NVRAM is manufactured with a built in battery which keeps power applied to the memory after power has been removed from the product.

Since the part operates as a normal high-speed memory part while power is applied, there is no delay when data is written into the device. These memory chips store the bits of data by blowing small fuses inside the memory device. Once they are programmed they cannot be changed.

These parts are found in many products and were a favorite in the United States Space Program because the data, once programmed, is immune to changes caused by radiation. Microcontrollers are usually found in products which perform a single function such as microwave ovens, computer printers, automatic sprinkler controllers, etc. A microcontroller normally has 40 or more pins since the input and output operations occur directly from the chip.

Since the microcontroller has internal memory, it is this memory area that you may read and program using a device programmer. HEX is short for hexidecimal. Hexidecimal is base Where humans are used to the decimal system base 10 with numbers 0 through 9, hex has the digits 0,1,2,3,4,5,6,7,8,9,A,B,C D,E, and F. Although this may appear confusing, the reason HEX was chosen is that it provides a simple way to represent 4 binary bits as a single digit.

The table below shows binary numbers and their hexadecimal equivalents.





27C64 - 27C64 64K EPROM Datasheet




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