This article includes an assembly language listing that requires MAC/65 or Atari Assembler Editor. You will also need access to an EPROM burner. The three earlier installments ran in the January, February and March 1985 issues of Antic. This USART design is a simplest case design. Writing to any address in the $D100-$D1FF range puts a character i
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nto the transmit buffer and it will be sent out the serial I/O line. Reading any address in the same range gets the last received character from the receive buffer. The easiest way to test this arrangement is to tie the serial input and output lines (USART pins 20 and 25) together. If you write a character to the transmit buffer and wait a few milliseconds, you should be able to read the same character from the receive buffer. All this assumes that we`re decoding addresses and that we have some software in ROM, so let`s get on with those details. The output signal $D8XX-$DFXX, combined with the Device Select signal (DEVSEL), provides the Math Pack Disable signal (MPD) to disable the floating point ROM in the CPU so it doesn`t contend with our ROM for the data bus. We can use the same signal to select our ROM. This allows us to remove some of the logic from last month`s circuit. Just remove the wires from 1C4 pins 6, 5, 4, 13, 12 and 11 and connect MPD to ROM pin 20. (See last month`s Figure 2). The signal $DlFF selects the Device Enable Latch. When a write signal clocks the 74HCT74 latch, the value of the Data 0 line (D0) will be stored. Writing 1 to address $DlFF selects our external device. Writing 0 deselects it. $DlFF can also be used later to select an interrupt register. By combining it with DEVSEL and $DlXX, we get a Device Register Enable signal (DRE). We`ll use this signal instead of part of the logic in last...
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....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
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....
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
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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