There are some important considerations to using more memory, but it certainly is possible. the mp3 player project uses 32 megabytes! But using more memory requires careful consideration. The most important factor is that the 8051 processor has a 16 bit address space. This means the processor can never `see` more than 64k of memory. Actually, the 8051 has three memory spaces, 256 bytes of internal RAM,
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and two 64k byte external spaces, one for data and the other for executable code. The executable code space is read-only (PSEN signal), so there is really only one writable 64k address space. This design uses an AND gate (74AC08) to combines the two spaces together, which makes the board simpler to use and of course is needed to allow writing to the memory during code download. So in the end, there is really only a 64k address space to use. A common approach to using more memory is to connect the memory as shown above, and then to connect the higher address bits (A16, A17, etc) to port pins. This is called "bank swapping", because it effectively provides multiple banks of memory and only one is "visible" to the processor at any one time. The banks are "swapped" by changing the port pins that connect to the upper address bits. In the schematic above, the 39F512 flash rom is actually 64k of memory, but only 30k is available to the user (the chip select logic does not assert CE, pin 22, so that the LCD, 82C55 and chip select signals can use the upper 2k of the memory map). A simple approach to using 60k of flash memory would be to disconnect A15 (pin 3) from +5V and attach it to one of the port pins. Likewise, a 39F040 chip could be substituted for the 39F512, and then A16, A17, and A18 could be attached to additional port pins to provide sixteen banks of 30k or a total of 480k of flash memory. A similar approach could be used...
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
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The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
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In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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