Hi again,
Just because in lab few weekl back my teacher told to write program, i have made code but the timmiming of it was not constand in oshonsoft stimulator.........!!
in this how you have calculated how many LED will work??
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How to Start hardware of 8085up......??
- Thread starter RITESH
- Start date
Hi again,
Just because in lab few weekl back my teacher told to write program, i have made code but the timmiming of it was not constand in oshonsoft stimulator.........!!
in this how you have calculated how many LED will work??
In that case, have you been asked to re-submit the assignment?
No, there is no simple equation (that I am aware of) providing that kind of answer. That was merely a suggestion, based on my own experience in embedded systems design..
Here's aother suggestion for you: try breaking down your problem by asking yourself some questions in the following order:
1.) How many LED's do I want to control for this project?
2.) What kind of interface circuit will I need to successfully control all those LED's from standard (usually multiple) 8-bit peripheral ports (as found on an 8155/8255 PPI or virtually any embedded microcontroller)?
3.) Based on the level of multiplexing, given by answering question 2 and also the total number of LEDs can I determine a suitable update rate?
4.) After reading through the 8085 user manual, will this CPU meet the display update rate given by question 3, remembering that I also have to include code to handle message scrolling?
What you need to understand here Ritesh, is that almost any 'seemingly large' problem can usually be broken down into smaller, simpler ones. My point here is to get you to 'think' in a certain way about any problem..
Another bit of advice I can give you as a student is to try and actually build as many different 'small' embedded projects as your budget allows (using PIC or 8085, it doesn't really matter). This will give you a better idea of what Problems you can solve with these devices.
Good Luck and have fun!
Regards Valentin
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I have written some info for it, pls see it is small doc till now what i have learn from sea.......!!
http://riteshelectronics.webstarts.com/project.html
per
Veteran Member
What I would do here, was to connect the inputs of the 7-output 4-bit driver to some I/O pins so that they can be programmed using the CPU, and then connect the clock input to a fifth I/O output. This way you can easily syncronize the output data to the display updates. You should also connect one of the CD4017 outputs to an I/O input; to allow the CPU to detect the state of the display. Of course you will have to use/assume 5V for everything connected to I/O.
If you decide to go with this solution, note that you will need to program the update speed into the CPU directly. The easy way would be to connect the clock output of the 555 to the interrupt input of the 8085 (you may have to invert it first to make this work correctly), and make the update display as an interrupt handler. The hard (and ineffective) way would be to program the display update-delay in software.
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per
Veteran Member
But it can be used with the 8085 in a very easy way. You don't have to re-invent the wheel for every car you make.
per
Veteran Member
A port is basically just a way for the CPU to controll digital electrical lines. For a port set to "output", the CPU can set it to either be a "zero" (Ground), or a "one" (+5V). Likewise, reading a port set to "input", will yield "zero" if the port is grounded and "one" if +5V is applied.
Think of it as a device the CPU uses to observe and control the state of digital logic. An outputs sets the state of a digital line, while an input observes the state of a digital line.
per
Veteran Member
What do you mean? Please explain a little more detailed.
Chuck(G)
25k Member
May I suggest that you take small steps before large ones? You might want to start with an Arduino board (inexpensive) that has roughly the same computation power as the 8085 system you're looking at. There are tons of projects using them on the web so you can learn how to put circuits together. After you have the knowledge about how one designs and builds peripheral circuitry, you can move on to building the CPU of your choice.
glitch
Veteran Member
That's a good suggestion, Chuck. I started with Microchip PIC microcontrollers before getting into designing an 8085-based system. I only really got interested in the 8085 when my I/O needs exceeded that of the lower-end DIP PICs.
I am just asking how to use port just like blinking led not in deep just for starting, i am not asking how to build CPU.
I have Quick start Propler microcontroler from paralax itself ( .spin lang) i am also learning it's programing.
per
Veteran Member
That's quite easy. All you have to do is to first invert the I/O output ports using a 74LS02 inverter, then you connect the negative poles of the LEDs to the 74LS02 inverted outputs, and the positive pole to +5V (remember to add appropriate resistors so the LEDs don't get too much current). When an I/O port is on, it will be inverted to a zero by the inverter, and the inverter's output will start draining current. Current will then folw through the LED, and the LED will light up. When an I/O port is off, the inverter will not drain it's output, so no current will folw through the LED.
Chuck(G)
25k Member
Assuming that we are still talking about the 8085, to create a usable I/O port, you need to decode and latch the output. There are several parts to this:
1. You need to decode the address. As data and address are multiplexed onto the same lines in an 8085, you need latch the address using the ALE as a strobe from AD0-AD7 That gets you an 8-bit address.
2. Then you can take this latched I/O address and decode it according to your needs. You can use a multiple-input AND gate, or a demultiplexer, or even a PAL.
3. You then need yet another latch, which is connected to AD0-AD7, whose chip select input is connected to the I/O address selected in (2) AND the IO/M* pin, using the falling edge of the WR* pin as a strobe.
I hope this answers your question.
1. You need to decode the address. As data and address are multiplexed onto the same lines in an 8085, you need latch the address using the ALE as a strobe from AD0-AD7 That gets you an 8-bit address.
2. Then you can take this latched I/O address and decode it according to your needs. You can use a multiple-input AND gate, or a demultiplexer, or even a PAL.
3. You then need yet another latch, which is connected to AD0-AD7, whose chip select input is connected to the I/O address selected in (2) AND the IO/M* pin, using the falling edge of the WR* pin as a strobe.
I hope this answers your question.